My opinion might be because I don't have much understanding of it as a framework, but from a non power user perspective, I've found the UX to be amazing.
The reason is that, like AMP, Apple News only supports a subset of HTML. It's up to the publishers to adhere to those limitations. Some choose not to make a special Apple version or change their main content to be Apple-friendly, so Apple News does what it can to show what it can.
It's not ideal, but it's better than being reliant on Google.
Also, if you see an article that doesn't look right, there's an option to report that article to Apple. One of the options is "Content missing."