I just announced the ox-hugo package. I love the blogging framework of Hugo, but disliked that I needed to manually take care of the post front matter and also noticed the shortcomings of writing in just Markdown. I also missed the tree-based text organization of Org mode. So this package was born.
Writing posts in Org mode gives you all the Org markup power (that's already more than Markdown), plus a lot more! like Org Babel, property inheritance, etc.
An example: I wrote this post ( https://scripter.co/notes/string-functions-nim-vs-python/ ) that's heavy with code blocks and results of evaluating those code blocks. It would be super-painful in Markdown to paste all the code blocks and also their results. In the Org source: https://gitlab.com/kaushalmodi/kaushalmodi.gitlab.io/raw/mas..., each of the #+RESULTS blocks in that Org source are auto generated using the Org Babel feature.
I elaborate more on why I use ox-hugo, or why I use Org for blogging in native Emacs environment here: https://ox-hugo.netlify.com/doc/why-ox-hugo/
Even if one is not using Emacs as their editor, as the OP mentions, the Org markup is simple enough that anyone can use their favorite editor to write in Org. To add to that, using a little Makefile, they can run Emacs in batch mode to take advantage of true Org mode features like Org Babel, etc.
For instance, one can clone the ox-hugo repo, https://github.com/kaushalmodi/ox-hugo/, and just run "make test" or "make doc" to let ox-hugo do its thing, without having anyone to know what to do after opening Emacs, what command to run, etc.
"make doc" will generate all the Markdown content needed for the entire documentation website that I linked in the very beginning of this comment, all from a single Org file.. You cannot do that in Markdown.