you can build a competitor dashboard! nip69 is open and anyone can list events, it's.up to your fantasy.
@mostro is 100% nostr based, anyone can be a mostro exchange, anyone is free to exhange shit money with sound money. That's Satoshi vision and we never have to forget this.
i can see some of the points you say, but forcing a user to have sats before trading is a barrier imo.
On communities and support i don't discuss i have no great experience on that. But i suppose, that robosata is mainly used in eu and lnp2p in latam, that users are really different. Just my opinion. Mostro could be set up from anyone with some tech skills , and fee is completely settable. Also 0 if you want.