As someone still using Facebook and eager to maintain something like it for the future, I decided to give
#Friendica a try, since it seems to be the only plausible option at the moment.
IMO a screen like this (where you end up when you try to join) is a dead end for 99% of users.
Again, IMO, the most important thing for Mastodon is having mastodon.social as the default way to join. Federation is important, but having an obvious choice of server is even more important, if the goal is growth.