[tgv]

XML is too unwieldy for human consumption. Editing it is error-prone, and those schema-directed editors are even worse, because everything requires clicking and clicking and clicking.

For machine-to-machine communication, it's very well suited, but most data is simple enough, and the XML libraries I've used tended to be --let's say-- over-engineered, while there are no hoops to jump through when you want to parse JSON.

And one thing I always disliked about XML was the CDATA section: it makes the message even harder to read, and it's not like you're going to use that binary data unparsed/unchecked.

XML just tried to formalize data transfer and description prematurely, which made it rigid and not even sufficiently powerful. I must say that XSLT and XPath were great additions, though.