Beehaw was around much before the current “population explosion” of the Fediverse, though, and by all accounts was doing just fine. Naturally it didn’t have as much content as it currently does, but the sort of reddit-esque content flood that some people seem to need really isn’t a requisite for sites to thrive.
I’m on a small lemmy/reddit -like content aggregator / forum that has maybe a few hundred users, and while it’s certainly quiet compared to Lemmy nowadays, it’s got a small active community and nobody feels like it would need more “volume” to be a nice place to be.