The admins of lemmy.world are generally opposed to defederating and have apparently announced via mastodon (i haven’t seen the official post but several comments have said) that they will wait and see what threads federation looks like before deciding whether or not to defederate.
Agreed, I’ve been on lemmy for like a month and already had to make several accounts on different instances because I’m just trying to see everything and instances keep defederating. I understand lemmy is young and growing fast and there will be growing pains, but threads isn’t even on activitypub yet and they’re already being blocked by half the instances.