Arctic (iOS and MacOS only, unfortunately) has built-in swipe actions for blocking and unblocking at the community and instance levels.
In addition to the standard federated community list, it also has a separate Lemmy community list that instead pulls its data from Lemmy Explorer. Since this instance doesn't use Lemmy Federate, it's both a useful means of finding communities that aren't federated to this one yet, and also a useful means of blocking any uninteresting or otherwise unwanted ones. You can then have it filter out communities you've blocked, to avoid having to scroll past them again after.
Took some time to decide which communities I did or didn't want, but down to 992 unblocked communities now, or hopefully 988-ish if instance-blocked ones can filtered out too.
Blocked it ๐
Two other communities on the list, one from feddit.rocks and one from lemm.ee, seem to be on the list too given that they're also unblockable, and should probably stay that way given that unlike the thunder one, they seem to target specific Lemmy users.
I guess I'll ask the Arctic developer if there's a way to detect instance-blocked communities to filter those two communities from my list as well.