World was already the biggest by far when I first started lurking back in July, and it’s just getting more dominant. Before, there was quite some diversity in the distribution of generic communities, but nowadays the vast majority of posts that reach the top are from over there.
I really can’t see any specific virtue that it has; uptime is not the best (or so I’ve heard), the moderation is quite lacking (which is demonstrated by the fact that Beehaw defederated them), they make some unpopular moderation choices (like blocking !piracy@lemmy.dbzer0.com), and overall the atmosphere is a lot less… nice than those of smaller instances.
I also feel like it goes against the idea of the Fediverse that one instance has control over most of the platform. Especially on Lemmy, where communities mean that building community within an instance makes so much more sense than elsewhere, and upvotes are federated near perfectly regardless the size of your instance, decentralisation makes a lot of sense. It really just doesn’t make sense to me that Lemmy World is where people are going.
As @Masimatutu points out, for a community on another instance, you normally only see the subscriber count of people from your own instance who are subscribed there, which can make other instances look smaller than they are.
I think you are right. Kbin now has multi-communities called Collections, and it’s a bit of a gamechanger.
We can make our own and/or follow other people’s public multis on various topics. I am now seeing so much more content from way more instances.