I quite liked it when it first came out, I'd been dealing with a ton of bespoke formats up until then. Pretty much every one was ambiguous and painful to deal with. It was a step forward being able to push people towards a standard for document transfer.
I suspect it was SOAP and WSDL that killed it for a lot of people though. That was a typical example of a technical solution looking for a problem and complete overkill for most people.
The whole namespace thing was probably a step too far as well.
That was a huge reason JSON took over.
Another reason was the overall XML ecosystem grew unwieldy and difficult to navigate: XPath, XSLT, SOAP, WSDL, Xpointer, XLink, SOAP, XForms... They all made sense in their own way, but it was difficult to master them all. That complexity, plus the poor ergonomics, is what paved the way for JSON to become preferred.