It really depends on the instance. There are many cozy, non-mainstream corners on the Fediverse. For instance, beehaw.org is as pleasant as can be.
masimatutu
By all means, fuck Meta to the moon and back, but for goodness' sake, users on federated servers can choose to block the domain with the same result, not to mention that admins can simply restrict it (see social.coop/@eloquence/1115888…). It just isn't so black and white as people are making it seem.
Federation with a bigger platform is realistically the only way for Fedi to become mainstream, and at the moment Meta seems at least to be trying to be communicative. And with their quite unvaluable userbase they really don't have enough leverage against the privacy-concious Fediverse to turn AP into MetaPub. For now.
Thing about the Fediverse is that software is just software; what you should care about is the instances. There are a whole bunch of Mastodon instances that have already defederated long ago. A few big ones include mas.to, mstdn.social and troet.cafe; you can find the rest here: fedipact.veganism.social/.
I'm just saying that even on federated instances the users can choose to block Threads, and that that gives the same result for them. There's no need to force the hand of the user; there are more than enough corpo-critical people on Fedi for it not to be taken over by Meta.
Edit: And I understand that allowing interaction with Meta is very risky business. Which is why I like the approach of instances like social.coop which restrict interaction from Threads but still give the user a choice.