The thing this oversees is that the interface is important, simpler is not worse, it can in fact often mean better. For example while docbook may have some technical, the user experience for someone who just wants to write some basic stuff is absolutely horrible.

If I imagine beginner-coding me, the first thing I would ask for example is why the hell not just use html by that point. Markdown is a thing I could peesent my non-technical parents unrendered and they still would be able to read the content, just fine for the most part. Try that with docbook.

Now nerds like to pretend the more powerful format is automatically superior. It isn't. Markdown is sucessful because it is so barebones and opinionated and because it forces a focus on the content over formatting. If that is what you need markdown is perfect. If it isn't, go for Latex, HTML+CSS, Typst or use InDesign or whatnot.