Comment by majewsky

Verbosity certainly is an issue with XML, but far from the only one. IMO the main problem of XML is that it was designed as a markup language, but then misused as a data structure serialization language. When used as a markup language, the distinction between attributes and children is meaningful. When serializing data structures, the dichotomy breaks down. For most subfields of a larger data structure, it's not obvious whether to serialize that subfield as an attribute or as a child. Contrast with JSON, which only consists of obvious data structures.