There are more ways to type (at schema and inline) and more types (see the common XSD types) available OOB in XML than JSON could ever have. Then we can introduce custom types. JSON looks rather impoverished in comparison.
Admittedly, XML isn't the most pleasant syntax to interact with by hand.
The main idea, however, was wonderful. An information exchange format (xml itself), a way to define schemas (xsd), a transformation language (xslt), and stylesheets (xsl?). I kind of miss it.
XSLT and XPath each went on to great solo careers, XSL-FO kind of fizzled when XML+XSL failed to displace HTML+CSS.
There's also XQuery for transformations and XSD/RelaxNG for schemas, the whole combination of XML database, WYSIWYG (via XSLT) XML editor and output transformations is very powerful, every journal we published and every site we ran at the British Medical Journal was generated that way.
A lot of really stupid JavaScript could be done fairly easily with XSLT natively inside a browser engine. An XML document can point to its own XSL(s) so get rendered to the appropriate delivery format or just used directly as data.
No, I'm pretty sure that if they have only used XML syntax as a data rep and not XML-associated tooling like XSD, they are quite aware that when thet say they hate XML they are talking about syntax.
OTOH. I am surprised at the number of people that seem to thing “has a schema language that can be used to specify structure beyond just the basic raw language” distinguishes XML from other data representation languages.
Or, more generally, the way that “if you don’t like XML, maybe your problem is you aren’t using enough of it” has become an edgy contrarian position rather than steretypical establishment enterprise consultant thing it was 15 or so years ago.