Ha, this is me. I did exactly that (with a community for the TV show Andor) and am guilty of the behaviour you describe.
I’ve probably been thinking along the same lines as you and OP though, 'cos I deleted the community a couple of days ago. I realized that if I had something more to say about that show, it doesn’t belong in it’s own niche community, or ‘Star Wars TV’, or ‘Star Wars’, or even ‘Television’. Perhaps a ‘Movies&TV’ comm, although - at this rate - maybe even ‘entertainment’ would be best.
I’m starting to think that instances that limit community creation to admins have the right idea (e.g. Beehaw, or - to use a non-federated example - tildes).
Some instances have started ‘Community Teams’, but I sense that anytime they discover a dead community, their instinct is to find ways to promote it, get new mods, drive engagement etc, whereas I’m more of the opinion that they should be nuked and consolidated (along the lines of what the ‘cooking’ communities have tried to do, I suppose).