I used ProseMirror back in the day (well over a year ago now) on a site I was working on and it ended up being a nightmare to maintain. It would break on every new version, screw up the build process, error constantly in mysterious ways that forced you to dive into the internals... At the time it was not designed with the state-view architecture either, making it harder to reason about.

I ended up scrapping it entirely for Quill and it was a massive relief.

In my opinion as a mostly-uneducated observer to this project, it is exactly the kind of project that would benefit massively from static type-checking. I can't count the number of times things broke on an upgrade because of simple bugs in the code where `undefined` would trickle through function calls or function interfaces were updated and other parts of the codebase were not updated in accordance. These are not hard problems to solve, but if you're dogmatic about using vanilla JS with as little build step as possible, you're going to run into these all the time.