Maybe they don't want to be a single community equal to all of Reddit. The goal is to be a
way to host the equivalent of a subreddit, which is not the same as a
place for that. There are many places, and many - including me - believe that's how it should be.
Also, blocking nodes in a distributed social network is neither new nor unhealthy. Usenet has killfiles. IRC has k-lines. Far from being injurious in themselves, they're essential tools to prevent some rando from setting up a bogus instance and using it to spray garbage all over everything. I already had to block one obvious ex-Redditor who had done exactly that on Mastodon, shitting all over a thread that had been going well until then. I was utterly unsurprised to see that they got defederated shortly afterward. That's what should happen when people can't stop misbehaving.
Do I wish that the fediverse had better moderation tools, both separate from defederation and for coordinating defederation decisions? Of course I do. AIUI coordination is done now - when it's done at all - with an ad hoc system based on tags, of all things, and that's a bit absurd. I have some ideas about how a better system might look or be implemented, but I certainly don't fault anyone for using the tools they have during a period of such rapid growth.