... simply defederating will not solve this (in most cases).
Oh it would address that concern, but it's a very heavy-handed action. At present, I don't think there's enough reason for instances to defed from Threads, even when there are good reasons for me to want myself to be. That really plays into my not jumping over to some instance which has already taken that step; I would wonder about how such an instance was being shepherded in other ways.
Once there are proven and reliable mobile apps for lemmy and kbin and whatever, the barrier to entry for the general public will be much lower. But the general public also needs to know that there are ways to get to fediverse content outside of the Meta environment. You and I and those like us here now are still pretty early adopters.