I still think the reason XML failed is largely because it's a document markup language not an object serialisation language, and 99% of the time you really want the latter.

You don't need attributes, you probably don't need namespaces, you probably do want at least basic types.

Look at this for example: https://docs.rs/serde-xml-rs/0.8.2/serde_xml_rs/#caveats

JSON solves all of that for serialisation. The only problem with JSON is it has ended up being used for configuration, and then you really need at least comments. I wish JSON5 was as well supported as JSON is.