Truly radical ideas have almost vanished from mainstream works. As a random example, the famous science fiction novel Stranger in a Strange Land, published in 1961, contains passages that pretty openly advocate for cannibalism. Time Enough for Love by the same author presents incestuous relationships as positive and completely normal. I dare you to show me anything comparable to that in today's literature.

You mean 60ties era famously tolerant to interracial relationships in literature or art in general? That is just example from top of head.

The Hays Code was in full force at that time, you might want to read it.

That has nothing to do with how radical the ideas presented in literature were. The 1960s were a cornucopia of literary exploration, massively expanding the horizon of what is thinkable.

The past 20 years have not only failed to contribute to this exploration, they have actually reversed some of the progress made back then, and lots of what had already been made thinkable is now unthinkable once more.