However, Marxism is just an abstraction that is related to the underlying epistemological disease of the modern era which is that we use statistics to prove our assumptions regardless of an actual identified mechanism of the phenomenon. We discard the search for the theory because it's hard and we've become accustomed to believing hand-wavy explanations for fields or social phenomenon we are not experts in. Arguably, nobody is an expert here though because there is lots of murky data about these particular topics that is widely dispersed and subject to heavy confirmation bias by researchers.
Instead of looking for the "why" we cargo cult and focus on the other side. IMHO, it's better to understand the "why" whether it's the why of the "ideal curve activist" or the meta-why of the observer of the "ideal curve activist" or the meta-meta-why of me observing your understanding of the issue. However, figuring out the "why" and seeing through statistical "facts" is the only way to really improve our understanding.
In the natural sciences this is easy. We have the scientific method. In the social sciences there is endless opportunity for subtle errors or coming to conclusions that are incorrect occasionally due to error but usually due to sometimes carefully constructed but almost always omission filled perceptions of reality.
Where I really see a problem is where social sciences interact with natural science and acts as a natural science in the eye of the beholder, which happens in macro economics and even sometimes in things like programming methodology.
The discourse of modern day feminism is best characterized by writers like Michel Foucault. Where discourse is viewed as a postmodern power play. Where the logical validity of the discourse is secondary to the function it serves in power relations.
No, it didn't. Feminism predates Marxism ; certainly, some strands of feminism were informed by Marxism in some way, and certainly there is a school of Feminist criticism that largely follows the same dialectic model as Marxist criticism (with the same understanding of the label but replaces the central struggle of the classes with one of the sexes), which split off from Marxist criticism as you describe, and which suffers from the same problem as Marxist criticism in that it is essentially takes the preeminence of a certain struggle as revealed unquestioned truth and reinterprets the world in light of that revelation.
Just like nobody cares that there are very-few/no male prostitutes or strippers.
The underclass you speak of is split along gender lines too - unfortunately.
Prostitution is very common in the gay and especially trans-gendered community. It may just take a different flavour of prostitution and a different sense of power balance.
The American Left are Jacobin libertines - they owe nothing in their program to Marxism.
And Marxist theory is definitely not "masculine" or "authoritarian". Marx was always critical of the family and stressed the fact that marriage was a form of exploitation, famously comparing it to prostitution. This is why many Marxists have called for the abolition of the family, and why Marxist-Feminism exists -- it's just an extension of dialectical materialism with primacy placed on gender relations.
Economic Marxists explained the ills of society through the conflict between rich capitalists and the poor working proletariat. The rise of the middle class threw it a curve ball that it couldn't explain and it fell out of favor (outside of the Soviet union and American academia).
Cultural Marxism uses the same conflict between dominant class and under class to explain social pathologies in the under class. Thus, we all hear about statistics where under classes are not meeting the same performance as the upper class, with the implication that it is the upper class's fault. This is called "oppression".
So we know that women make less than men, but we don't hear much about how men are falling behind in college degrees and high-school education because this does not fit the Marxist narrative.
Furthermore, when there is an underrepresentation of an underclass in some desirable area, we take that to be de facto evidence of oppression (nobody cares that there are no female garbage collectors or miners). We all except the collective guilt for the sins of our class and nobody questions whether or not the Marxist narrative might just be fundamentally flawed.
Modern academic feminism and racial theories are based on Marxist models, which causes them to make many errors of reasoning IMO. There is also a lot of data that they can not explain. For example, racial Marxists have no problem explaining why some minority races do worse in school than white children (oppression!). But I've yet to hear an explanation from a Marxist as to how other minority groups (Asians) do way better than white children.