Slop.

It's really telling how much of a non-falsifiable orthodoxy liberalism / capitalism / liberal democracy is to these people

And that's the really ironic thing! Liberal academics will call Marxism/historical-materialism "unfalsifiable" because we try to apply a class-based lens to understanding events while both modern economics and liberal political theory basically start and stop with the observation that humans are agents optimizing based on a set of preferences. Like okay, sure, humans are optimizing some utility objective, but that doesn't tell you anything! You could say that about any action ever! Marxism is a structural analysis of why we hold the preferences we do, why we take the actions we do, and how those evolve with economic relations, technology, culture, etc. This is why we go much further than just hand-waving everything as being the result of good/bad people doing good/bad things.