Fedi client app developers need to design fedi client apps in a holistic way to include a custom server (as with Mammoth's moth.social) or create an account for the user on one of a curated selection of other servers, without forcing the user to choose one.

It's a severe problem with trying to grow fedi that general users are expected to understand how servers work and make an informed decision about which one to join. General users don't care about this topic and will quickly turn away when it is forced upon them. That's why the client app needs to handle this for the user without making a fuss about it.

These apps also need good discovery features and feeds with posts that are trending generally and for specific topics. Then devs need to make money with those apps somehow, then they need to market those apps (at this point, it goes beyond just "devs" and expands into an organization with a marketing department, etc.).

Then, hopefully fedi's inherent advantages of interoperability and resilience will naturally cause people to choose these user-friendly, effectively marketed fedi client apps over things like Instagram, Tiktok, etc. After all, if it can't compete on its own merits with all other factors being equal, there's no point to it for most people.