So, what can be done?
1. Tell new people to use third party apps, they are better anyway and have more features. More info at https://fedi.tips/which-apps-can-i-use-should-i-use-the-official-app-or-a-third-party-app/
2. Tell people to sign up on the website. Mastodon's official site at https://joinmastodon.org is still asking people to choose a server, and is very professionally laid out. (I've also got my own amateurish effort at https://fedi.garden.)
3. If you're comfortable using github, give a thumbs up at https://github.com/mastodon/mastodon-ios/issues/1023
(6/6)