I understand your concern, currently Nostr is a bit of an echo-chamber, and I think this is absolutely normal for a newborn technology and its related group. But you have to look at the potential. The real point is that it is not a platform, but first and foremost a protocol, so you can build whatever you want. The more applications that are created, the more people will flock, and these people will join other nostr-powered services creating a more wide and heterogeneous public, where you could find *your* public.
All this require works, from all parties, even the creators. If you think you can find a better and healthy ecosystem than Twitter or Instagram, for free, you are right to be delusional.