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.
People figured out everyone doesn’t need to use the same exact X to have access to the same things X provides many times throughout civilization. Maybe the join page needs to communicate it better, but also people need to try to figure it out.