marx was right about a lot, but not everything - especially considering that material conditions have drastically changed from his time, including digital technologies, the internet, television, nuclear weapons, robots, mobile phones.
many more classes than the bourgeoisie and proletariat have sprouted up due to the expansion of the means and modes of production, and the increasing specialised nature of many facets of modern life. the west has massively de-industrialised and is not going to return to antiquated models of the industrial factory floor being the basis of social relations.
this doesnt mean an abandonment of marxism, but an advancement from it - otherwise you will be stuck in the 19th century.
its not helpful to contemporary subjects to just say "read marx" as if this is the redpill that allows you to see the matrix of today's postmodern simulacrum - things really have developed and cannot be simply be disregarded as superstructural illusions hiding a binary class division.
so, learn to think about today's experience.
We already have Post-Marxism. With Laclau et al and all the post-structuralists. Analytical Marxism could be counted as a Post-Marxist movement proper, even Freudomarxism could be counted as Post-Marxism. There are just so many currents in Leftist thought its hard to keep track with all of them
it all feeds into the progress of theory
and theory of progress