is very far away from perfection
Confusingly, you seem to have taken this from Karl Voit's website, without referencing having done so?
https://karl-voit.at/2017/09/23/orgmode-as-markup-only/
And then taken the sentence out of context. His point is that even though there isn't a formal Org-mode syntax definition, there is an informal one in that all of the Org mode syntax elements are part of the Emacs Org-mode implementation. The latest Org-mode implementation /is/ the spec. This is in comparison with Markdown where there are numerous syntax definitions and no implementation which includes all elements and everything is a mess.
> This is in comparison with Markdown
This context is irrelevant, I'm not discussing how bad markdown is, but how great org mode is.
> The latest Org-mode implementation /is/ the spec.
You're just conflating the terms, that's not what a spec is, and having one has benefits that living impls don't have
You can start a "document" at any place in the org hierachy. I would rather prefer a distintion between these two concepts.
With regards to your 80% claim, do you happen to know an extension that works well with pasting images from clipboard?
Over the years, my professional note taking has become extremely reliant on quickly pasting images (most often screenshots from papers or quick-and-dirty plots I made myself) from clipboard directly into the notes. The friction of doing this in vanilla org-mode is the only reason I'm not doing everything in org-mode.
It has ingrained itself so deeply into my muscle memory that I built out a whole website builder [1] and extended the language to support all kinds of nice QoL things for my website [2].
Something that as the other commenter here noted—I can rely on orgmode for many decades to come.
[1] https://github.com/thecsw/darkness [2] https://sandyuraz.com