Think about it; instead of those in charge or the instances deciding who they don’t want to be federated with and thus restricting content for the users, it would be better if users were able to block entire instances instead.
We’d be able to curate our own browsing experience so much better without admin/mod drama influencing the rest of us.
Edit: Alright so maybe not exactly replace defederation, but it should still be an option available to us, and in general should become the default action before defederation IMHO.
I mean, federating with an instance doesn’t necessarily mean you NEED to have it added to the default feeds.
It could theoretically be done in such a way that it only shows content from the communities you are subscribed to, and never show content from that instance in general feeds, for example.
Or it could even be done in such a way that instance blocking is enabled by default for every user, and each user has to opt in to see content from other instances outside of maybe a selected curated few that might be allowed by default.