I agree with the monothematic problem, it is probably the most common complaint of nostr.
I quite like the example of zbd, a client-community which defaults to its own community as the main feed. Although it it would take quite a dedication for a community to make their own app it is at least possible and perhaps makes more sense than a relay/ 'community' (for now at least).
Could then have the option of following these 'clients' even.
Obviously I have no idea what I am saying and I'm being uncharacteristically optimistic.