Most of the Internet ifra depends on libxml2, major vendors like Juniper and Cisco use it.
To my knowledge Android use it as well,
Naturally, with the advancement of AI, one would expect XML would be first thing to rewrite, given that library is in the critical path literally everywhere.
Clearly that's not the use you have for a new XML library. It's a use you're imagining somebody else would have for it. And because you're just imagining the use case, you've failed to think through what "good" would actually mean in that use case.
To replace libxml2 across these ecosystems you would need it to be API-, ABI, and probably bug-compatible with a decrepit old C library. That's not something anyone or anything can write from just the XML spec.
Your original point would have had a bigger impact if you hadn’t married it to an idiosyncratic affection for XML. Now you’re stuck defending the usefulness of that particular technology which is entirely unrelated to AI.
And if you don't need one, why write one? If there is no specific use case in mind, how do you even determine what dimension "good" is measured on?