That's still built on top of the hardcoded vim design choices though.
For example, I really like the "select then edit" approach of Helix, but Vim doesn't really play nice with that (there may be better plugins since I last looked to be fair). File handling, buffer rendering, and frames have very little to do with that, and yet I have to switch editors, lose all my plugins and configurations, and switch all those subsystems at once.
There's missed opportunities for modularization.
Edit: looks like Neovim is already split from its UI.
You're right that changing the whole editing model will involve rewriting a lot of keybindings. You could do that in vim if you really wanted to -- start by remapping motions to enter visual mode first. I don't really know why you'd want that when visual mode is already a keystroke away, but that's ok.
FWIW though if that's what's important to you, I get the sense that kakoune is much more vim-like in making it easy to compose with other tools, while being set up for your preferred editing model.