EDIT: Just crossed 26000!
Almost! At the time of this post, lemmy.world has a whopping 25733 users and is growing fast.
Since my last post yesterday, it has added 4000 new users, making it the clear second-largest lemmy instance out there. Also quickly catching up to lemmy.ml's 36000 (not taking new signups).
beehaw.org (3rd largest) sits at 12500 users, partly because of more restrictive registration requirements.
Source: https://lemmy.fediverse.observer/list
Exciting to see all this growth!
you're right that a large majority of people do not care, but this mentality will begin to change at some point. Also, the entire point of this is that it doesn't matter where the users are, because they can still join the same communities. Now, there are obviously a lot of things that need to improve in lemmy to make it more usable, but federation isn't one of them. The ActivityPub protocol is simple, yet powerful and relatively scalable.