Markdown is severely limiting for prose and blogging though and leads to unsemantic element abuse or having to do a lot of manual HTML markup (which with no controls over styles means you’re limited further). There aren’t good conventions for a lot of ‘normal’ concepts like admonitions, figures, definition lists, citing blockquotes, footnotes, table of contents, etc.
Another red flag to me is supporting GitHub-flavored Markdown over CommonMark which actually tries to follow good standards practice for everyone. Instead projects like Pandoc have to work hard on alternative parsers because GitHub does whatever it wants with little regard for CommonMark's RFC, and in some cases, even basic semantic HMTL.