No one, not even the lemmy.world admins, are suggesting that. In this very thread they’ve mentioned imminent plans to educate new users about other instances during the sign-up process.
Then we take that as an opportunity to educate them instead of tricking them out into believing that it is a good idea to put them all in the same server.
Nobody is being tricked here, and you need a seriously warped view of the situation to think otherwise.
They will also go back to reddit if they join a server that is constantly having outages.
You’re still making the same incorrect assumption that your original post made, that the stability issues are even tangentially related to user count instead of ongoing attacks. But again - new users figure out federation within a few days. If the outages bother them they’re smart enough to know they can try a different instance and now likely have the experience needed to know which one may be the best fit for them.