Markdown handles complexity by allowing html to be freely put into the doc. The basics are really easy, and if you need to do something more advanced html exists. Though this can sometimes make readability drop to 0. I ended up doing this for a complex table I wanted in a readme file, and kind of regret it. I have to explain to people on my team how to use preview mode in their editor, or to view it in the repo online. Although that view online does look nice.
I mean it’s the same problem with mermaid but I still use that pretty religiously. Being able to have your README natively render graphs is super useful and most engineers these days have a markdown previewer built in to the software they use eg vscode
