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 would add that the risk of joining a small server is that the owner can suddenly delete them at any time and you would have to start all over again elsewhere. Best thing to do is to make an account on the large instances only.
Mine has existed for a few years now, so I’m fairly confident it’ll exist for more