I think markdown would work precisely because of this. Word is too hard to use and too easy to create documents that are impossible to edit by a second person.

For context. I've just watched my wife trying for 20 minutes to add one item to a bullet list, with the proper indentation and numbering of course. Mission impossible.

That problem wouldn't exist in Markdown. There is no way to accidentally do an unmodifiable list of list in a table indented by spaces.

Of course any user adoption would require a decent editor software with live preview and export to PDF.