Usenet was like that, except forums could federate their articles, and their targeted selection of groups depended on what er... groups they were willing to host. People started getting spammed though, and started protecting themselves using PGP to recognize each other and avoid spammers. And the corporates were like "ohhhh no," and went full disinfo campaign to get people to not do that.
Independent unfederated web forums were sort of a coping mechanism for that pressure. Something that sorta worked, and didn't threaten the corporate hegemony, so corporates tolerated it, because they could take their time scheming how to destroy forums without any risk of anyone stopping them. That's when they started promoting MySpace then Facebook, and everything went predictably downhill from there.
And yeah IRC outlived both Usenet and Web Forums, but then got killed by Discord.
That's been my experience at least.
