I wasn't going to answer this because I didn't want to spark the wrong kind of argument in the thread, and because it would take a scary amount of time. But I ran across an old comment where I wrote about it: https://news.ycombinator.com/item?id=713432. Those are still my views.

I would be a little kinder to the postmodernists if I were writing that today. That might be because another 11 years have gone by since I actually had to read them. Memory becomes more like imagination over time, and I'm probably imagining a version of them that I like better.

The important thing is that the things they called fictions and illusions largely are fictions and illusions. They embedded these insights in a nihilistic frame that is ultimately unhelpful, but the contributions are still valuable. It's a bit like seeing how a magic trick works: once you see it, you can't unsee it, and you become able to see the same trick in the future—except in this case the "magic tricks" are rationalizations that humans use to hide things, justify things, pretend things. That phenomenon is challenging to look at and goes much deeper than it appears to. The useful way to work with it, though, is to apply it to oneself.