> Feminism split off from Marxism in the 2nd wave of the 60's/70's when it was decided that class based oppression is a derivative product of patriarchy. Gender took the center stage to class, race, and other forms of marginalization.

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.