I don't say that you are wrong.
But strangely, Usenet also had hundreds if not thousands of topics with one interface, but I believe it was killed by forums.
Unlike Facebook & Co, Usenet was decentralised. If the next Cloudflare bug or something different blocks Facebook, then nothing is working. With Usenet at least some of the servers might still work.
And Usenet servers probably weren't used to spy on every detail of the life of its users (and in the case of Facebook even non-users). Here different forums have the advantage that one might only reveal part of oneself, not the full picture.
But I admit that I also stopped using Usenet out of convenience, and because some of the groups simply weren't frequented anymore.