Personally, I’m not a huge fan of instance-level defederation as a concept. I’d rather leave it up to individual users to block certain instances/users/communities if they don’t like them. Otherwise you get a situation where admins can go on a power trip of blocking instances or users that they don’t like for petty reasons or just because that instance and it’s users don’t subscribe to the group think of the day.
I really like the fediverse, but this whole “instances blocking other instances” seems like a good way to kill it quickly, or create useless echo chambers that are as bad if not worse than the centralized platforms that people are seeking to avoid.
Free speech means having to deal with some bad apples from time to time. Even if people are saying things you don’t agree with, you need to remember that that also means that you’re allowed to say things that others might not agree with without being silenced.
The problem is who decides when an instance contains “nothing of value”? You’re leaving that up to a small handful of admins. You could also encounter a situation where multiple admins collectively decide to defederate from anyone who doesn’t subscribe to the same block list, so any instances who hold different opinions are cut off from loads of content on other instances. We run the risk of splitting the fediverse up into multiple, totally isolated chunks which I don’t think is a good thing on the whole.