I think it would definitely be nice to spread users (and communities) across more instances. Doubly so since I’m on an instance that is struggling with the volume of content from Lemmy.world because of what is effectively a limit of how much you can get from one instance at a time.
But if we want people on Lemmy who don’t know what Linux is, then we need to avoid that massive barrier of asking users to pick an instance. And the second massive barrier of registration applications.
A good compromise I think would be to have multiple trusted servers with open registrations that the app randomly defaults them to when they go to sign up for an account.