I've written about this before, from the deductive side. Hegelian dialectic, in addition to being crappy philosophy, is pseudoscience by its very nature when made into the backbone of any scientific theory. (This sets aside the issue that economics in general at the time of Karl Marx was close to pseudoscience.)

Now, we have something new from the inductive and empirical side. Joe Costello, whose dad droned decades as a hollowed out (Eliot's Hollow Men) factor worker, notes that Marx's definition of who the Industrial proletariat is (or was in Marx's time) was totally made up, trying to apply Roman peasant farming to the 19th century industrial world.

Understanding the history of labor, socialism, and Marx is like opening one of those Russian Matryoshka dolls, one nestled inside the other. Obviously, the industrial labor force was created by industrialism. However, socialism's agrarian roots preceded industrialization. Marx used industrialization to redefine socialism, wrongly claiming his socialism was scientific as opposed to its “utopian” forebears.

Marx's thinking had all sorts of wrong headed ideas and fatal flaws. First, in one of the great misreading’s of history, he relabeled industrial labor, “the proletariat.” A term derived from the Ancient Roman republic, proletariat was a census designation for economically disenfranchised citizens, who did nothing but “reproduce.” For most of the republic's history, Rome was largely comprised of small farmer citizens, but as its empire grew, land ownership was increasingly consolidated. Ever more in debt and away fighting the latest war, the majority of small farmers lost their land to ever larger entities, then ended up in Rome. Here they became the proletariat, an economically disenfranchised, politically enfranchised citizenry reliant on the state for food, housing, and entertainment.

Costello doesn't stop there, though.

He also faults "the Old Moor" for not considering inputs beyond labor, most notably energy. Given how steam power launched the Industrial Revolution, this is a worthy ding. He also notes that capitalistic change, and capitalistic control, extends far beyond the "means of production." Give the whole thing a read.

Back on my site, there's also the angle of the "no true Scotsman" card being played by Marxists today.