Earlier quoted context omitted.
I would suggest introducing two things. First, introduce The Diataxis framework ( https://diataxis.fr/ ) for documentation. It makes people think about documentation in a more structured way, and allows you to be more specific in the types of missing documentation. (High documentation cultures are often good with explanation but not tutorials, for example.) Second, I would introduct the idea of a Documentation Portfo…
I'm sure these are great technological answers but this problem can be solved simply and quickly by a human. Not every issue needs to be solved by a butter robot. Why not employ a technical writer/documenter/whatever job title you like, even as a temp, whose sole job is to sort out the mess of documentation you have and then to write new documentation as you move forward?
This isn’t the case for external documentation, that has to be more polished, needs sign offs and images and demos and stuff - tech writers can come in useful here