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!
Someone explained it a little better in another post. It will not erase my content. So if I’m logged in under my lemm.ee account but post on a lemmy.world instance. If for some reason lemm.ee got defederized, my post or comments would still be there at lemmy.world I would just not be able to use my lemm.ee account going forward.
It seems like this is the way to go like OP says