Yeah, I think communities have a completely different goal than social media feeds.

Social media is about "getting seen", "maximizing reach", "grandstanding". It is, by definition, inclusive. Try to get as big of an audience, as possible, and maintain their attention by feeding their excitement. Dopamine hits and yelling around and status conflicts and BIG REVEALS and follower counts.

Communities is about "meeting with the like-minded" and "finding people I want to converse with about X" and "seeking out deep convos and expert opinions". It is, by definition, exclusive. Try to raise the signal as high as possible, while lowering the noise as low as possible, by being selective in the membership. A community anyone can join is, by definition, not a community. It's a hashtag.