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.
Having something there would definitely be wise I think, given how many people are apparently just being sent links direct to a specific instance to sign up (and therefore skipping join-lemmy entirely). But it would need to be very short, to the point, and sum things up in a way non-techy folks can immediately understand. In my experience so far, a lot of people here struggle to explain the basic concept without writing a whole esseay about it, and nobody is gonna read a wall of text on the signup page.