I think a small, somewhat homogeneous community is very attractive. You get a high ratio of interesting posts and very little toxic behavior.
The problem is those communities never scale. Maybe they can't scale. Technology won't solve this problem (because it is not a technology problem). Moderation also won't solve the problem (IMHO) because it's either too expensive at scale, or it just imposes the homogeneous viewpoint of a subset of the community.
Maybe the balkanization of social media is the best we can hope for.