What else?

I want figures. I want linked references. I want custom styling for images, and for blocks of text (eg warnings, notes, etc). I want a TOC and numbered chapters and sections. Sometimes I want a bibliography. Or a table generated from data within a JSON file.

You don't need this stuff for a readme file. But IMO markdown isn't powerful enough for blog posts, documentation or longer form content.

I use docusaurus as markdown renderer which adds most of what you need. Mermaid.js for figures. Never needed a data table from JSON but would be easy to add a custom component for this.

So yes for me markdown is definitely powerful enough for blogging and complex technical writing - has been for the last 6 years- with a few small extensions and I’ll eat my hat before I use anything xml based or reinvent html…