I agree, I feel similarly. There are now 25+ car groups on fbook that I have to subscribe to, because the main web-board / usenet group for that car doesn't get anywhere near as much traffic as it used to. Major vendors are providing support on fbook - which sucks.

See, I'm the opposite. I've got a Discord server, which are very much "where my friends are": If I make an acquaintance (or any of my friends do), they get added to the server. Some stick around, and get woven into the social fiber. Some never come back, and eventually get removed from the server during our annual purge. There's maybe 10-20 active people (i.e., people we see at least a couple times a month), a handful of regulars that are that multiple times a week, and then maybe twice all that again of people we hear from once in a blue moon. If I want to chat, I'll hop in voice. If I want to share something I found, I'll stick it in a text channel.

There's still plenty of communities on the internet. It's just that the communities worth belonging to are not wide open to the public. Community building does not scale.

Reminds me of https://diewithme.online/ which I just learned about.

Not exactly the same as your idea, but definitely in the same vein of "only available under a certain condition"

The SomethingAwful forums have been $10 to join since 2001. If you get banned, that's another $10 needed for a new account. Has worked pretty well for 24 years.