In fairness Apple did come up with a custom JSON format for articles:
https://developer.apple.com/documentation/applenewsformat
The problem is that people don't use it. I imagine it's a chicken/egg thing, the audience on News isn't big so it isn't worth the publishers time catering to an entirely new format, the News experience is crappy so the audience doesn't grow.
They could have insisted that everyone use their format but I suspect publishers would just refuse. It's not exactly in a publishers interest to help boost a middleman between their content and readers.
I'd be really interested to see what Apple's approach would be if they used more web technologies (since that's what publishers are using today anyway). Even just a webview with disabled JavaScript would get a ton of the way there in terms of performance. They have WebKit engineers in house that could probably tweak it even further.
It’s almost like Google AMP was a good idea and solving this problem this community had a melt down over it.
It's definitely that publishers don't want it.
This is actually the trajectory of both Apple News and iAd before it, which is what started out providing the ad service for Apple News. Apple would like to do a high quality solution, and then keeps relaxing their standards when there's not enough buy-in from the content providers. They were forced to allow the non-curated news formats to have sufficient content.