What is a nostr dating app? If it's an app and not a protocol, what do you need nostr for? A dating app but with nostr login?
Maybe something like "Bang with Friends" but with some fancy crypto such that third parties can't figure out what's going on?

If you make it a protocol, you won't have the direct financial incentive to develop it. Of course, you could tap into the nostr social connections to offer these matches in a centralized DB that you could monetize. If you just want to see it happen on nostr, poke DOWN to do on nostr what they stopped doing on Facebook ;)