And it is working fantastically so far, both for shooing users and new devs away :).

I try not to get into preference debates (been writing software for over 20 years, and by year 7 I had stopped defending mine). So let’s take the "most mature standard for schema specification" at face value and be pragmatic about it. It’s not like folks will rewrite all of Nostr to use a different format anyway.

Regardless, the payload schema is just a small part of an API specification, and there’s absolutely nothing stopping anyone from using JSON Schema with something like AsyncAPI. In fact, this is one of the most common choices. A good reason to use a popular spec like this is that 9 out of 10 times, someone has already done the hard work for you.