Are you talking about Jordan Peterson's concoction of "Marxist postmodernism"? Peterson's a dilettante and a demagogue, and Marx seems to me closer to scientism than to postmodern obfuscation.

Marx's account of alienation is interesting, but he said we're alienated from our labour, not from life in general or that there's ennui even outside the workplace. The existentialist's concept of alienation is much broader, I think. But yes, Marxism might be consistent with this exitentialism, so there were early-modern forerunners.