Turing complete? Not really, parsing still forms static data structures in linear time. The fundamental screw-up with XML is that it was a textual markup forma

Turing complete? Not really, parsing still forms static data structures in linear time. The fundamental screw-up with XML is that it was a textual markup format (e.g. HTML or word processor documents) that got usurped for cross platform data transfer. Among many other problems, that put pressure on its design to be unambiguous to generalized tools - which wasn't an initial design consideration. So you had an awful lot of making people use document markup processing tools to serialize and parse data structures, schema and transform systems that tried to target both mindsets and did a bit of a poor job at each, and lots and lots of abstractions to try to make it so you only had to deal with the problem once. Even JSON is a bit of a pain the farther away from late-bound or untyped scripting languages you get.