When I last played with it (Emacs + Org) I had options enabled which hid much of the markup entirely (e.g. the **) and applied various styles to express the intended structure, and it was lovely, much more than just coloring. Nothing I'm saying is without love for Emacs and Org, more just sulky acceptance that tools can add additional mental overhead, even if they're cool, and this seems to be the opinion/philosophy of modern tools etc, VSCode/IDEs/Web-based IDEs etc.
So.... when I tried to use Org in VSCode, Vim, Notepad etc, it just sucked. Not even a comparison. In that case, Markdown was better. Maybe I'll look at it again. But like the OP (in the sense of making up my own thing) I have dabbled in creating my own clone of Org-mode based on a Markdown spec.
Hmm ok, I never have these options on. For no particular reasons other than that they don't seem to be the default (or something's wrong with my config), and I never missed any additional application of style.
So it's possible that I just got very much used to how org-mode "source" looks.
So.... when I tried to use Org in VSCode, Vim, Notepad etc, it just sucked. Not even a comparison. In that case, Markdown was better. Maybe I'll look at it again. But like the OP (in the sense of making up my own thing) I have dabbled in creating my own clone of Org-mode based on a Markdown spec.