Personally I thought first impressions of Mastodon (and Lemmy) were abysmal. Being told to pick a server without knowing what that means or the consequences of that choice just scares people away. Unless someone has a specific server in mind they should not even be asked to pick one. Instead a number of existing servers should volunteer as curated core servers and new users are automatically assigned to one of those. There can still be a "let me choose" link that goes to a full list of servers if they prefer to browse them all