The overwhelming majority of people that criticize post-modernism have little-or-no actual knowledge of it. Foucault can indeed be difficult to understand, but make no mistake, he does have interesting things to say.
Many who criticize post-modernism (and Foucault) aren't really criticizing the philosophy, but the understanding of that philosophy among groups who have adopted it for political ends.
When people say "post-modernism sucks" they mean, for example, that moral relativism sucks, or that it is stupid to view science as a grand narrative of no more value than other narratives. When they say "Foucault sucks" they are attacking the understanding among the "woke" of how power relations work in society, an understanding that is drawn, however incompetently, from readings of Foucault.
Leading post-modern philosophers didn't embrace those positions in an uncomplicated way, but many influenced by them do, and they massively outnumber the people who have actually bothered to read Derrida or Baudrillard.
Furthermore, many post-modern philosophers were showboaters who enjoyed being provocative, so you don't have to look hard to find justification for the unnuanced understanding of their work.
A word currently used to describe "consciousness" and being aware of the truth behind things "the man" doesn't want you to know i.e. classism, racism...
No argument there. Even a critic like Roger Scruton who has read him writes "Whatever you think of Foucault (and Rorty), there is no doubt that they were intelligent writers and genuine scholars with a distinctive vision of reality. They opened the way to fakes but were not fakes themselves. Matters are quite otherwise with many of their contemporaries."
To name names, he means Lacan and Althusser among many others.
Many thousands of people have read Marx, all of his works. More important, his basic ideas are clear and understandable.
Marx believed that history was driven by the means of production, and that the original means, foraging, produced societies that were egalitarian and peaceful. Then the human race switched to agriculture, and societies became unequal, oppressive, and militaristic. This went on for thousands of years, until finally some societies switched to industrialization and capitalism, which upended the old social order, but lead to new forms of oppression and suffering. But capitalism has internal contradictions that will lead to its being overthrown by the workers and replaced with anarchistic socialism which will be egalitarian and peaceful. And so everyone should join in and support the overthrow of capitalism.
That is all clear and understandable, and that is not an accident, because Marx's goal was to change the world through mass political action, and the only way that can happen is if you have a set of ideas that is understandable to ordinary people.
And that leads me back to Foucault. If is ideas are so complex and subtle that only a tiny elite of dedicated scholars can understand them, then they are of little use in helping people overcome the many things wrong in the world today.
When people say "post-modernism sucks" they mean, for example, that moral relativism sucks, or that it is stupid to view science as a grand narrative of no more value than other narratives. When they say "Foucault sucks" they are attacking the understanding among the "woke" of how power relations work in society, an understanding that is drawn, however incompetently, from readings of Foucault.
Leading post-modern philosophers didn't embrace those positions in an uncomplicated way, but many influenced by them do, and they massively outnumber the people who have actually bothered to read Derrida or Baudrillard.
Furthermore, many post-modern philosophers were showboaters who enjoyed being provocative, so you don't have to look hard to find justification for the unnuanced understanding of their work.