The big issue would be to get everyone to sign up for something like that though. Since things have been running for a while without any sort of checks like that, it would be difficult to switch to that system now (do you merge communities with conflicting names, do you let them change their name, do you let them delete the community, etc.). Plus there’s the whole nature of the fediverse where every instance can be customized to the creator’s needs (so one instance might want to be on that database and others might) and it just becomes too much work to get everyone on board.

Maybe I’m wrong and someone will eventually implement something like this and people will want to use it, but I very much doubt it from what I’ve seen of the fediverse so far