what's wrong with XML? Maven XML is a configuration not a programming language.
Maven files have a simple conventional structure and a defined schema. Once you learn it, it's a breeze to work with. It's not like you need to write hundreds of lines of SOAP or XLST — which is actually why people started to dislike XML, and not because XML inherently bad.
Edit: I'd also take XML over TOML any day, especially when it comes to nested objects and arrays.