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.
Lemmy would crash if you fed it everything, that’s why Lemmy.ml and lemmy.world were crashing so often since May, the SQL did not scale. Some of those problems have been fixed, but it was performing really badly at the time of the Reddit API cutoff.
The admin headaches of a full feed from over a thousand unknown sources means you are opening yourself up to a lot of legal, copyright, porn, vote manipulation, unpredictable load surges, etc. I think it would have to be something people fund a lemmy site that promises to carry everything.