> post-modernism, a direct offshoot of Marxism

The communists manifesto says

"Our epoch, the epoch of the bourgeoisie, possesses, however, this distinct feature: it has simplified class antagonisms. Society as a whole is more and more splitting up into two great hostile camps, into two great classes directly facing each other — Bourgeoisie and Proletariat."

This grand narrative and ideology spoken with objective certainty with regards to binary oppositions, is the complete opposite of postmodernism.

Milton Friedman's works in a similar vein although on the other side are the opposite of postmodernism as well.