I don't understand why blocking (or "defederating") instances is such a core part of the design of lemmy but not actually supported on a per-user basis.
Defederating is core to the fediverse. Lemmy just uses a shared protocol to exchange content. And as others have said, Kbin has instancr blocking, community/magazine blocking, and user blocking. You could just create an account on a Kbin instance if it's important enough. You still get to see the same things.
Kbin has instance blocking, community/magazine blocking, and user blocking.
Kbin doesn't have instance blocking yet, just domain blocking, which is for hiding posts that link to a particular domain. Domain blocking is also bugged right now, and will just hide random stuff from you.
I mean, if you want to get technical, none of them have any blocking really. Blocking on any fediverse is generally just the equivalent of muting/hiding.
Wasn't aware of the bug though (as I haven't tried the feature yet, but probably wouldn't have a way to notice anyway).