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.
I’m not a lemmy.world user (so I have no dog in this debate) but I’m gonna disagree. I’m of the opinion that signups for an instance should stay open as long as the admins can afford/handle the growth. I think it’s unfair to force the admins to keep it open if they aren’t able to handle it which is the crux of what OP is asking.
Besides, it’s not like those users cant just federate with all the communities of lemmy.world they want. And I bet there won’t be a dearth of choices for decent instances if the demand calls for it. Lemmy.ml closed signups despite being the big instance at one point in time and lemmy.world emerged as an alternative. So why wouldn’t something similar happen if lemmy.world did the same?