Really weird to see this person mention MyST as a form of Markdown, and then go on to talk about reStructuredText as their first example of a markup language "that gives you more control over structure than ... markdown".
The whole point of MyST is to provide a markdown-like alternative to rST. It literally has directives, roles, structural semantics, etc. It just doesn't have the unlearnable syntax of rST and the so-called governance of docutils (the de facto rST parser) (see e.g. discussion on https://github.com/sphinx-doc/sphinx/issues/8039 and linking issues)
The whole point of MyST is to provide a markdown-like alternative to rST. It literally has directives, roles, structural semantics, etc. It just doesn't have the unlearnable syntax of rST and the so-called governance of docutils (the de facto rST parser) (see e.g. discussion on https://github.com/sphinx-doc/sphinx/issues/8039 and linking issues)