How you read the relationship between Ukraine and the early Soviet Union is contingent on how you interpret the civil war from the spring of 1918 to 1921. Following February 1917, Ukraine had demanded national autonomy, and indeed in summer 1917 the provisional government had granted the right of self rule in (parts of contemporary) Ukraine. But by December 1917 (after the October Revolution), the Bolsheviks claimed Ukraine and precipitated uprisings across the country, which quickly led to war between the fledgling states: both Bolshevik and Ukrainian Soviets claimed authority to rule. By February 1918, the Bolsheviks had seized Kiev, and the Ukrainian government had fled; in turn Ukraine received aid from Germany and the Austro-Hungarian Empire in exchange for supporting the continuing war effort, but after only a few months Germany installed the Hetmanate puppet government as an explicitly anti-communist regime. The Hetmanate was overthrown in December 1918 by Ukrainian revolutionaries bolstered by Bolshevik Russians; this group, the Directorate, established the Ukrainian National Republic once more.
In January 1919, the Bolsheviks launched an invasion of Ukraine; Kiev was seized in February, and much of the country was under Bolshevik control by late Spring. Peasant rebellions against Bolshevik brutality and manpower limitations from the Bolsheviks led to the White Army seizing much of Ukraine during the summer, with severe fighting in Crimea and the southern front ultimately leading to the relatively bloodless loss of Kiev to the White Army in late summer. By the winter, after again vicious fighting on the left bank, Kiev was taken by the Bolsheviks. Fighting continued until 1922, with the second winter campaign of 1921 the largest major resistance against Bolshevik control of Ukraine. Sporadic resistance continued throughout the 1920s as well.
This is a simplification (leaving out some additional back-and-forth, the role of Poland, and so on), but should highlight just how complicated the control of Ukraine was during the Civil War. A reasonable case for Soviet control of Ukraine against the White Army can be made, while it is inarguable that a once-independent Ukrainian socialist state repelled the Bolsheviks. How, also, you interpret the Bolshevik policy of korenizatsiya, the state support for Ukrainian language and culture (in contrast to Imperial repression of both), or the intentionality behind the Holodomor, flavors how you see the early Soviet relationship with Ukraine.
Interpreting Imperial Russia and the Soviet Union as colonial empires has a long tradition (unsurprisingly, the exiled Ukrainian leaders of the early 1920s claimed as much) that has recently been revisited--Francine Hirsch's Empire of Nations for the USSR and Alexander Morrison's The Russian Conquest of Central Asia for the Russian Empire explore the colonial relationships of the Russian state.
Many of the Cold War paradigms of pre-Soviet history are really rather schematic and rigid, and Soviet historiography and self-assessment can be quite poor for a variety of reasons. Western funding for Slavic studies has dried up after the dissolution of the USSR and the archival access of the 1990s has been limited more recently, so many of the finer questions aren't likely to be resolved.
I don't see any consensus on whether these relationships fit the definition of colonialism, but I think the scholarship is trending that way (particularly for the Russian Empire, which I am more familiar with).
This is a very complicated one, and no two historians will agree exactly. However, I can give a bit of an answer as it relates to the Soviet period, and particularly the early USSR in the 1920s and 1930s. The aspect of imperialism that your quotation is hinting at is primarily the cultural one, not the economic, by which I mean that if the Soviet Union is perceived as an empire in its behavior in Ukraine, we're interested in how its cultural policy shaped Ukrainian identity. The economic relationship is something I'm not as comfortable commenting on, though I am willing to say that Ukraine was one of the more productive SSRs on average over the entire period, and often did put more wealth into the Soviet GDP than it received in investment — for what little that metric is actually worth.
At any rate, speaking of the cultural and political relationship of the state to Ukraine, I would start by asking us to recognize that we can't really speak of a single Ukrainian identity, as a mass phenomenon, until some time into the period I'm about to talk about. Ukrainian identity certainly existed, and many people felt very strongly that they were Ukrainian and not Russian, and had done so for decades if not a century or more. Given the charged political context of this thread, which I can't pretend to ignore, I want to be very clear that Ukrainian identity was not simply invented by the Soviet state. That said, until the 1920s and 1930s it was largely an elite phenomenon, limited to the intelligentsia.
To take an example, if you were to go to what was then the western Ukrainian borderlands with Poland and ask a peasant what their "nationality" was, they probably would have given you a blank stare. They might have a Polish-sounding last name, or be Catholic, or profess Uniate confession, but are they Polish? Are they Ukrainian? To them, these terms aren't exactly meaningless, but they're not relevant in daily life. What language do they speak? Well, they speak "in the simple way," or "as we speak here," and given how you express grammatically your ability to speak languages in the various languages and dialects of the Eastern Slavic continuum, that's as good an answer as any. (In Russian, for example, you might say you speak "po-russki," literally "in the Russian way" — in these local dialects, "po-prostomu," meaning "simply," is no less valid.)
So despite the early Soviet state's enthusiasm for giving the former subject peoples of the Russian Empire cultural self-determination under the political guidance of the Soviet pyramid structure, they ran into quite some difficulty trying to figure out just who was to have what cultural self-determination. That hypothetical peasant above is representative of much of rural Ukraine. Language was hardly a good metric, as it was all a broad continuum between the cultural centers of the intelligentsia; faith was a jumble from village to village and even house to house; custom was little better; last names were almost meaningless in the face of all this confusion. People we would now categorize as Ukrainians, Belarusians, Poles, Russians, Germans, and Jews all lived in a patchwork of villages where none of this particularly mattered in daily life.
The state had to do something, though, to uphold its ideological commitments. Stalin was strongly influenced by Lenin's writings on the intersection of capitalism and imperialism, and on the necessity of ethnic self-determination in a communist society. As People's Commissar for Nationalities, he had developed the classic Soviet definition of a nation as "a historically constituted, stable community of people, formed on the basis of a common language, territory, economic life, and psychological make-up manifested in a common culture."
On the basis of this definition, which emphasized a "common territory", the state instituted a policy, korenizatsiya or nativization, designed to encourage, or you might say force, the ethnic groups of the USSR to practice their ethnicities properly and in relatively contiguous geographic blocks. The goal was to teach all the nationalities pride, independence, and the capacity for self-government, which meant in practice creating administrative regions throughout the USSR for each ethnicity, in which newspapers and schools would be in the local language and local cuisine, dress, etc. would be fostered. As this definition and the programs of korenizatsiya ran up against the complexity of the borderlands, the state decided on a single identity on each village and made up for anything else it couldn't handle through with forced relocations and school programs that homogenized students to fit into their region's titular ethnicity.
All of this actually worked, to some extent. The state was moderately successful in convincing local rural peoples to adopt cosmopolitan understandings of their own ethnicity. Not perfectly, by any means — the dialect continuum and local customs remain resilient to this day, but there was definitely some buy-in. National identity didn't necessarily replace other identities of place and economic role until decades later, but people accepted these new roles while maintaining their own agency and their traditions where they could and where it suited them.
If anything, though, the state saw itself as having achieved more success than was either arguably accurate, or desirable. The state had always been afraid of these identities being used as tools of separatist nationalism or foreign imperialist encirclement, but with the rise of a military dictatorship in Poland and resistance to collectivization growing in the late 1920s and early 1930s, visions of rebellion overshadowed the idealistic hopes of Lenin's formulation. In the mid-30s, the state cracked down on many of the forms of national expression it had just recently promoted, abolishing autonomous regions and prosecuting displays of national pride. Though it didn't lead to any outright armed resistance, this did cause demonstrations throughout villages in the borderlands. These demonstrations were primarily in response to the forced collectivization of agriculture throughout, but later on, I think it's fair to say that they incorporated a degree of a national element. By saying it was something to be prosecuted for, the state strengthened this identity, if anything — though, again, not to the point that it became most people's primary form of identification.
So how are we to understand this? Ukrainian identity was not "created" out of nowhere by the Soviet state, as I believe Vladimir Putin recently claimed in a televised address, but its modern, widespread form is indeed in large part due to the policies the USSR instituted in the 1920s and 1930s. This, I want to be clear, does not make it necessarily illegitimate — throughout the USSR, national identities only really became widespread and popular phenomena at this time, regardless of whether they were Russian or Ukrainian or not. If we are worried about any policy being unjust at this time, I would say, it's not that the Soviet state supposedly created "false" identities — it's that the Soviet state suppressed real ones that did not conform to our current definition of nationality.
On the HOLODOMOR:
Anyway, on to a very controversial and traumatic subject, namely the Holodomor ("Death by Starvation"), the famine of 1930-1934, with the worst happening in late 1932 - early 1933. There has been a persistent political and historic conversation over whether this was a genocide.
First, it helps to review what the legal definition of genocide is, at least according to the 1948 United Nations Convention of the Prevention and Punishment of the Crime of Genocide:
"Any of the following acts committed with intent to destroy, in whole or in part, a national, ethnical, racial or religious group, as such: killing members of the group; causing serious bodily or mental harm to members of the group; deliberately inflicting on the group conditions of life calculated to bring about its physical destruction in whole or in part; imposing measures intended to prevent births within the group; [and] forcibly transferring children of the group to another group."
Now a couple things to say about the UN definition: there is a heavy focus on intent, meaning that for an act to qualify as genocide (as opposed to "merely" a crime against humanity), there has to be an intention to wipe out a national/ethnic/religious/racial group. There are arguments that this bar (largely set by the Holocaust) is too high. It's also worth noting that the 1948 UN language was determined with Soviet input, and so by definition the language approved by the Soviet government intentionally was designed to not immediately put them in legal issues (even though the person who coined the phrase, Rafael Lemkin, specifically had the mass deaths in Ukraine in mind). It's also important to note that there are other concepts of what concepts a genocide, notably "cultural genocide", as discussed in this excellent AskHistorians Podcast episode.
Olga Andriewsky wrote an excellent literature review in 2015 for East/West: A Journal of Ukrainian Studies on the historiography of studying the Holodomor, so I'm going to lean heavily on that for this part of the answer. She notes that the conclusions of James Mace in his U.S. Commission’s Report to Congress in April 1988 hold up pretty well. She notes that all Ukrainian presidents (except for President Yanukovich), favored official commemoration and historic of the Holodomor as a planned genocide, going back to Ukraine's first president, Leonid Kravchuk (who was Ukrainian Supreme Soviet Chairman and a longtime Communist Party member, so hardly some sort of anti-Soviet political dissident). "Holodomor as genocide" has effectively been the Ukrainian government's position since independence, as well as the position of many (not all) Ukrainian historians. Further research since 1991 that they feel has buttressed that view is that forced grain requisitions by the Soviet government involved collective punishment ("blacklisting", which was essentially blockading) of noncomplying villages, the sealing of the Ukrainian SSR's borders in 1932 to prevent famine refugees from leaving, and Stalin ignoring and overriding Ukrainian Communist Party requests for famine relief, and mass purges of the same party leaders as "counter-revolutionary" elements in the same year. Andriewsky notes that while some prominent Ukrainian historians, such as Valerii Soldatenko, dispute the use of the term genocide, they are in agreement with the proponents around the basic timeline, number of victims, and centrality of Soviet government policy - the debate is largely around intent.
So more or less open-and-shut, right? Well, not so fast, because now we should bring in the perspective from Russian and Soviet historians. Again, they will not differ drastically from Holodomor historians on the number of victims or the centrality of government policies (no serious historians will argue that it was a famine caused by natural factors alone), nor will they deny that Ukraine suffered heavily.
But their context and point of view will differ tremendously from Ukrainian Holodomor historians in that they will note that the 1931-1933 famine was not limited to Ukraine, but also affected the Russian Central Black Earth region, Volga Valley, North Caucasus, and Kazakhstan. This map from page xxii in Stephen Kotkin's Stalin: Waiting for Hitler, 1929-1941 will give some sense of the geographic extent of the famine. In fact, while most of the famine victims were in Ukraine (some 3.5 million out of a population of 33 million), some 5-7 million died from the famine across the Union, and Ukraine was not the worst hit republic in relative terms - that misfortune befell Kazakhstan (then the Kazakh ASSR), where some 1.2 to 1.4 million of the over 4 million ethnic Kazakh population died through "denomadization" and the resulting famine. At least ten million people across the Union suffered severe malnutrition and starvation without dying, and food was scarce even in major cities like Leningrad and Moscow (although on the other hand, they did not face mass mortality). Kotkin very clearly states: "there was no 'Ukrainian' famine; the famine was Soviet."
Other factors tend to mitigate the idea that it was a planned attempt to specifically wipe out the Ukrainians as a people - the Ukrainian borders with Russia were sealed, but this came in the same period where internal passports were introduced across the USSR in an effort to control rural emigration into cities (many of these were kulaks and famine refugees), and deny them urban services and rations.
Stephen Wheatcroft and Michael Ellman are two historians worth mentioning here, notably because they had a public debate about a decade ago around how much Stalin knew and intended as consequences during the famine. Wheatcroft argued that, in effect, the mass deaths caused by forced grain requisitions were the result of governmental callousness: unrealistic requisitions were set, including the punitive collection of seed grain in 1932. But in Wheatcroft et al's opinion, this wasn't specifically meant to punish peasants. Essentially, extremely flawed grain reserves policies (plus the elimination of any private market for grain) meant that millions of lives were lost. Ellman, in contrast, takes a harder line: that Stalin considered peasants claiming starvation to be "wreckers" more or less conducting a "go-slow" strike against the government, and also notes Stalin's refusal to accept international famine relief (which was markedly different from Russian famines in 1891 or 1921-22). But Wheatcroft and Ellman, for their disagreement, do agree that the famine wasn't an engineered attempt to deliberately cause mass deaths - it was an attempt to extract grain reserves from the peasantry for foreign export and for feeding urban industrial workers.
Ellman comes down on the position that the famine isn't a genocide according to the UN definition, but is in a more relaxed definition. Specifically he cites the de-Ukrainianization of the Kuban region in the North Caucasus as an example of cultural genocide. But even here he notes that while under a relaxed definition the Holodomor would be a genocide, it would only be one of others (including the famine in Kazakhstan, which I wrote about in this answer and I think has a stronger claim to the genocide label than the Holodomor, as well as the mass deportations and executions in various "national operations". He also notes that the relaxed definition would see plenty of other states, such as the UK, US, Netherlands, Portugal and Spain, similarly guilty of genocides, and in the case of Australia he considers even the strict UN definition to be applicable. Which would make the Holodomor a crime of genocide, but in a definition that recognizes genocide as depressingly common and not unique to the Soviet experience.
