I think you have it backward. Libraries like zod exist _because_ JSON is so ubiquitous. Someone could just as easily implement a zod for XML. I’m not a huge proponent of XML (hard to write, hard to parse), but what you describe are not technical limitations of the format.

I think that you're missing that the parent poster and I are implicitly assuming that XML is validated the most common way, i.e. with XSD, and that I'm comparing XSD validation and Zod.