Meta announced that users on Threads will be able to see fediverse replies on other posts besides their own. In addition, posts that originated through the Threads API, like those created via third-party apps and scheduling services, will now be syndicated to the fediverse.
Having no defederation is not being treated as adults, it’s just a free for all. User-specific blocking is not adequate for stopping bad influences on the fediverse and simply can’t do the same as instance-level defederation.
Preferring no defederation at all is akin to “free speech absolutism” - it asserts that anyone can say anything and anyone else can just choose to not listen individually. But that’s not really a good path for a welcoming and understanding environment.