You can. This is exactly what Flutter does, as I've commented on that thread you refer to on HN. It uses the Skia renderer that is like a 2d game engine to draw all the elements on the screen. They've had to reimplement everything though, like text fields and accessibility, so perhaps this is why it's not done more often.
To be fair this is what Electron does too via the browsers. It's just doing it via the worse possible way by leveraging technology that's awful for building UIs. I'm a fan of flutter they're definitely onto something. I hope they can bring it to the desktop in a way that works well too.
