XML is fantastic. XML with XSD and XSL(T) was godly for data flow systems. I mean, just having a well defined, verifiable date type was magical and something seemingly unfathomable for so many other formats.

What hurt XML was the ecosystem of overly complex shit that just sullied the whole space. Namespaces were a disaster, and when firms would layer many namespaces into one use it just turned it into a magnificent mess that became impossible to manually generate or verify. And then poorly thought out garbage specs like SOAP just made everyone want to toss all of it into the garbage bin, and XML became collateral damage of kickback against terrible standards.