I disagree. I have been writing man pages for a while, and mastering the language is hard. The documentation for both mdoc and mandb format is not covering the whole language, and the only remaining reference for roff itself seems to be the book by Brian Kernigham. mdoc and mandb are like a macro set on top of roff.

Just this week i considered proposing to $distro to convert all manpages to markdown as part of the build process, and then use a markdown renderer on the shipped system to display them. This would allow the distro to stop shipping *roff per default.

Markdown profits from the much larger amount of tooling. There are a ton of WYSIWYG editors that would allow non-technical users to write such documentation. I imagine we would all profit if creating manual pages was that easy.

On the other side, Markdown is even less formalized. Its like 15 different dialects from different programs that differ in their feature sets and parsing rules. I do not believe things like "How do i quote an asterisk or underscore so it is rendered verbatim" can be portably achieved in Markdown.