I agree -- the FOMO thing is real.
However having a clear path to follow would really help capture/retain those users. In other words "Wow, Lemmy is so popular it can't handle the traffic -- here's an up-to-date list of instances to try anyway", or some other option.
Possibly a pinned post where instance owners can comment info on their own instances without having to wait for someone to update a master list?
A pinned post like "Welcome to Lemmy!" on Lemmy.ml and other instances with that link would help I think. Also, I think it would be a more streamlined experience (and less disorienting) if the "Join" links on that page went directly to the instance's signup page instead of the local instance feed.