It's really fine for casual documentation. I wouldn't write a book or a paper in it though.
Technical papers with formulae and complex references are slightly more detailed, but that ends up being gloss. Even LaTeX for a simple text is quite minimal (though you need the starting template).
Source: I've made something of a hobby of marking up source docs into HTML, LaTeX, and Markdown. Of the set, Markdown would be my first go-to, and I've used it for some book-length projects.
Example here: https://ello.co/dredmorbius/post/lhw2eq4qmnnwxijlcrfyba
I would probably use org-mode for that.