To support decentralization and spread, should lemmy.world close registration at some point to prevent a performance overload due to too many users? Of course, if registration is disabled, there could be a hint placed somewhere near that from other instances you can interact with content on lemmy.world just like you had registered on it. There could be a link to join-lemmys instance overview.
Not all instances are going to be equal in terms of things like stability and uptime. It’s going to be unfair and frustrating to users who might randomly end up on a bad instance. It might work if it only chose along the top x instances or something, to ensure a bit of reliability for new users.