Agreed about the dying online communities. Part of all online communities are network effects: a forum is only as good as the users on it; and if all the users are on Reddit and Facebook, it makes it far, far harder to find interesting independent communities to join
Anyone can start their own subreddit and attract users. And you get high quality UI for free. Or I could spend weeks setting up my own forum software. Why would I do that?
Facebook et al won because they made things easy. I don’t like FB’s approach to privacy or dark patterns, but those aren’t why they won. Running your own website is a demanding hobby for tech nerds. Running your own FB group, anyone can do. This is because FB makes money from making it easy. “The web” doesn’t make money from making it easy, so it isn’t.
In addition, the open web is open to spammers. That’s why Google’s search results are degrading. Walled gardens cut down on these negative externalities.
Do you actually use reddit? It's an extremely cancerous experience on mobile, they actively work on making the ui as inconvenient as possible. Every iteration of reddits ui is even slower than the last one, which I consider quite an achievement considering how slow it was months ago already.
Reddit also has the "gold" thing going which is probably not what you'd want for your own forum, where some users are more equal than others because they paid money to an entity you have a questionable relationship with.
Unrelated: Google's results decline in quality because google values engagement more than quality. It's been like this for years. When you are the monopoly, you can easily trade quality for more money without negative consequences.
I spend a lot of time there, but the day "old.reddit.com" stops working is the day I walk away. The newer interface is unusable in comparison to the original and I will not be forced to take such a massive step backwards.
I get it, but besides making it easy, FB made online communities worse. They have absurd limitations that you only realize once you're in too deep. For whatever reason, for example, nudity is banned even in private groups on FB, so several photography groups I know are trying to go back to forums and blogs, but can't migrate their content, nor get most people to cooperate, so many of them are juggling multiple FB accounts because they keep getting temp-banned (and I'm not talking porn here - these are actual photographers that are regularly featured in big galleries).
There was also a game dev group that died out because FB kept flagging their users for spam. Turns out posting executables makes it think you're spamming viruses, even though it's just a gane prototype you want feedback on.
Finally, the quality of discussion is worse no matter what the content is, as FB forces the post>comments relationship, with comments being way less visible and usable than a top-level post.
And this isn't just one grumpy programmer screaming into the void - I only know about that because friends and relatives (from young to quite old) keep complaining to me and asking me for workaround to these limitations. Of course, the answer "just use something other than FB" is rarely accepted.
I wonder if a modern discussion platform with Facebook as the login provider (and some deeper integration of content, perhaps?) would help bridge this gap?