I would love a "better Doxygen", or more accurately a nice multi-repo, multi-language documentation generator. It would have almost zero config to get started,

I would love a "better Doxygen", or more accurately a nice multi-repo, multi-language documentation generator. It would have almost zero config to get started, but highly customisable. It would support (or be open to easy extension) both "classic" as "modern" and/or niche languages, from Java, C, JS to Python, Go, Nim, Haskell and Crystal. The generated documentation should look modern and exportable to both static HTML for online hosting and to some agnostic format, like JSON for further processing.