That exact argument works for most communities to defederate from. "Federate with everyone unless I take issue with the community or how it's run".
Plenty of other communities will federate with Threads, I don't have any problem with lemmy.ml opting out.
We'll get to see if defederating with Threads makes post and discussion quality higher than in communities federated with Threads, or if it only stunts the growth of this instance.
The Liftoff app allows this behaviour of combining multiple local feeds (even without logging in).