For liberals, the "problem" with marxism is that Marxism ignores the superstructure of society and only looks at the base. They will then point to the existence and influence of the superstructure as a refutation of Marxism.

I have literally never seen a liberal ever even comprehend the idea that the superstructure of a society is shaped by its base. That is what Marxism actually is. Do they think Marx did not understand gender, racial or religious discrimination? Or course he did. He talks at lenght about these things.

Some of Marx and Engel's most famous texts, like "the origin of private property, the state and family", for example, studies the emergence of the patriarchy.

But he does so from a material standpoint. That is what grounds his analysis at every point.

We must understand that the value of the Marxist philosophical project is that it is never content to simply accept the existence of things as they are by relying on notions of some "human nature", "god", or any such ideological nonsense.

It is similar to how you cannot truly understand how computers work, in all of their intricacies, without understanding how a transistor works. Liberals are people who refuse to acknowledge the transistor. For them, their computer is the magic box which dispenses treats.