> XSLT 2 was 2007, a year before HTML 5 was a thing, yet it never got picked up by browsers. Javascript was just easier to understand than XSLT.

Turns out that tasks easily done by programming languages are best done by programming languages. Who knew?

JSON allowing frontends and backends to communicate in a way analogous to the "smart endpoints, dumb pipes" model for networking saved the Web. The XML adherents wanted the inverted model, which was always insanely difficult to reason about and led to entirely XML-specific security threats.