I do think they will essentially die. They will morph into completely different websites, but I think they will be around for a long time, and I think their userbase won’t shrink even a bit.
Big websites are slowly adopting the facebook model: All the content is hidden and requires you login to view it. Creating an account requires some sort of personally identifying information like a phone number, photo of ID, mailing address, etc.
The old model simply turned out to be unprofitable. It was always done under the motto of “bring the people and the money will come” and so they made it as easy as possible to build up a large user base, but it turns out that motto is false on the internet, and investors have finally realized it. There is no point in having a massive user base if they don’t actually generate a profit for you. Anonymous internet users do not do this. They are indistinguishable from bots. If they don’t use adblock, they don’t click on ads. They don’t donate money. Yet they use up the majority of the server resources.
It used to be that you at least needed anonymous users to generate content for you, but (in part thanks to facebok) non-anonymous usage of the internet has become normalized. If anything the best content will come from someone who has their real name, and profile picture attached to the content they submit. The anonymous nobody is much less likely to post anything valuable.
I think the internet as we know it is dead, and tbh I don’t even blame big corporations for this. I blame mass tech illiteracy, and people’s willingness to sacrifice their privacy for some dopamine hits.
Usenet is still around.
It’s not a site but an actual system and predates (by quite a lot) the Web.
It’s was the social media equivalent back in the old days of the early 90s Internet (before AOL linked to it, before the WWW, even before Gopher).
After that came IRC (which funnilly enough is also still around, along with modern clones of it such as Discord) as well as online forums (which themselves are the descendants of the old BBSs, minus the whole modem comms part).
So far in my experience, the only tech that “dies” (well, there often is a handful of people who still do it for fun) is that which is tied to specific hardware (i.e. you don’t really have BBSs anymore because people don’t use modems to connect to a central systems via the phone line anymore) as pure software can live forever on top of emulators or just be reimplemented whilst preserving core features.