This sort of stuff is crucial and needs to be built in.
Most instances are one user's whim away from going away. This isn't a problem as long as clients back things up and migration is easy. But, that doesn't happen right now.
Guarantee we'll see some big news at points in the future when a big instance goes down because the owner died or just lost interest.
Again, these are easily overcome, but they are issues right now.
Well, I just made hobbit.world and intend to only have Tolkien related communities there. So block away if that's not your thing. However, the only way to block an instance is to defederate and that's kind of harsh. Hopefully the feature of blocking communities by instance is added.