Well if you don't do that, you would only have a lowest common denominator system with none of the advanced features, and the world has enough of those.
If I wanted to emulate a fraction of org-mode features I use daily in markdown, I would have to use Obsidian with a bunch of plugins, and we would end up in same boat.
I don't know the exact spec situation, but I know that comprehensive parsing libraries in modern non-elisp languages exist. An org-mode contributor has one in Julia[1], another in Dart[2] that powers a Flutter app, and there are many tree-sitter grammar based tools that are useable from neovim (e.g. [3]). The basic org2html or org2pdf CLI needs are already addressed by Pandoc.
[1] https://github.com/tecosaur/Org.jl