There are many lemmy instances in the world, but currently most people are using lemmy.world. This is why everything has gotten so slow.
You don’t have to delete your lemmy.world account, but check out https://lemmy.fediverse.observer/map it’s a geo-based map of lemmy instances – explore stuff nearest you, pick one, sign up, search , subscribe and begin interacting with your favorite communities. It’s easy, free and it will be faster. Try it!
I think the concerns about smaller instances are valid (as I post from lemmus.org). Some additional data points to consider when evaluating an instance would be whether they’re running a recent version and the uptime of the instance.
It’d probably be a good idea to have a page that promotes these smaller instances that ‘score’ well to help distribute some of the load.