Wow. It scares me that you know all of that.

Bad documentation is bad documentation whether it's in a picture or in text.

I have found that most software engineers get so hung up on UML notation of their diagrams that they end up never doing any because it takes too much effort.

Start with simply and succintly writing what the software does COMPLEMENTED by a diagram. Not the other way around.

Diagrams on their own are useless without some accompanying explanation. Ever read a book full of diagrams?