XML is still the implementation tool for Microsoft Office and Open Office docs. I wouldn't hold those up as the gold standard or anything, but it's hard to see how Markdown could capture everything that XML does for, say, powerpoint or excel.

> XML is still the implementation tool for Microsoft Office and Open Office docs.

It is and that is a good thing. I can't tell you the number of times that an application storing it's data in XML has made it possible for me to do things that would otherwise be impossible.

But nobody authors these documents in XML. It's just an application storage format. It could just as easily be Sqlite.

Unfortunately Word documents are XML. Microsoft has a LOT of customisation going on, but at the core it's very ugly, incredibly complex xml :(

Source: https://learn.microsoft.com/en-us/office/open-xml/word/worki...

There's also HTML, LaTeX and Typst for documents. I don't think that there is a clear winner here.