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.
Join-lemmy was different at the time. There were only a few instances listed, and most of them where either quite selective in their registration, completely closed, or open. LW was among the last ones.
There was also the trend (and I did it as well) to tell Reddit users to “just go to LW, it’s like Reddit” to avoid having to confuse them with federation.
Back when i made this account, lemmy.ml was i think one of the only instances with an active user count in the triple digits, and sopuli had single digits