If we are going to be mainstream, we really need an app that abstracts away most of the technical aspects of Lemmy.

Sure, you and I might understand federation and like it - your average user will see this wall of text explaining how it works as a brick wall and give up.

So an app that just says something like "pick a server, don't worry you can still see content from others, here's our suggestion" and then "create an account and login" will work as even many games work like this.

Then the main feed needs to be abstracted away, replace long URLs with "community name" and let users subscribe and browse without any subdivisions (unless they want to filter it out). Make sure the interface treats everything as if it were a simple subreddit, they see a group about a game they enjoy and they subscribe - no friction.