Another not-a-website submission, but Usenet with actual discussions. Web forums still annoy me compared to the elegance of Usenet, with hierarchical categories and sophisticated client software that can do things like score and filter.
I agree; NNTP is much better. I just started using Usenet last year, actually (with client software I wrote myself, because I wanted a command-line interface and support for SQLite, and other programs don't do those two things).
https://en.wikipedia.org/wiki/Eternal_September the whole Internet feels like the Eternal September to me. It all got dumbed down.