I started a community in the current implementation (librearts) so I'm familiar, but people are working on community specific relays. These would let relay owners moderate their own relays more completely. The makers of nostr all have talked about smaller vs bigger relays being the focus. They don't want a system with just a couple relays that everyone's on because it hurts the decentralization and sustainability, but what that means in a global view is that you're not sure who's going to see what you post similar to the issue with mastodon, and that problem extends to the current implementation of communities. For global view this is less of a big deal since you are generally just posting very general things out to anyone following, but for communities, you want to rely in the fact that the whole community can see it including strangers who don't grow you. Community relays fix this issue. People subscribe to relays/communities that they want that can then be smaller relays (or groups of relays for redundancy), but can also be sure that everyone in that community will see the post. And the reason we would want an app is to create the best first experience where you are seeing things you like, and also it would be needed because it's a totally different app concept to the Twitter-replacement app that we're on now. This would be an app more akin to Reddit or Lemmy but with proper architecture where each community can govern itself, be a paid relay, or complete with another community. And an app would just help people sign up and pick topics/communities they like, and then they would immediate have a main feed of strangers posting about things they actually are interested in. The communities could assist choose to be secret and not report to any people running a directory/app. It solves the problem of too big relays, helps the problem of discovering things you like from people you don't even know to look up, and makes them onboarding process easy to get an app tailored to your interests.