> setting up a new documentation is very easy with Sphinx
As per my original comment, the idea that documentation should require some kind of external markdown static site generator is bizarro land.
Sphinx starts from the point of view that you're going to write your documentation as if you were writing a book, then on top of that it has some optional features for pulling in information from source files.
Most of the others start from the view that you're autogenerating documentation from source-code comments, and on top of that there are some optional features for pulling in some extra content from documentation-specific files.
I think the Sphinx way tends to produce better documentation in the long run, but it takes more effort to get to something just-about-adequate.