The problem with XML is that it’s horrible to manually read and write, and it takes more effort to parse too. It’s a massive spec which contains footguns (a fair few CVEs exist just because of people using XML on publicly accessible endpoints).
Now I do think there is a need for the complexity supported by XML to exist, but 99% of the time JSON or similar is good enough while being easy to work with.
That all said, XHTML was amazing. I’d have loved to see XHTML become the standard for web markup. But alas that wasn’t to be.
I doubt this is really meaningful. It's not like browsers are forgiving about malformed javascript. We live with "tough, the developer screwed up" every day.
Now I do think there is a need for the complexity supported by XML to exist, but 99% of the time JSON or similar is good enough while being easy to work with.
That all said, XHTML was amazing. I’d have loved to see XHTML become the standard for web markup. But alas that wasn’t to be.