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!
The benefit for you is that you will be in a low traffic instance. All the content you load will be loaded from that instance, not lemmy.world. So for you the content loads faster.
Like, I’m replying to you from lemmygrad.ml, and I’m never actually connecting to lemmy.world, and no content is loaded in real time from Lemmy.world. this comment will be synced back to lemmy.world and then synced out to everyone else that’s subscribed.
But if 90% of people are on Lemmy.world then naturally it’s going to run like ass.