I went down that road for awhile. You start running into problems when you research all of the default behavior that the built-in widgets have, and this is even before you get to accessibility issues.
I love the idea of punting on HTML and writing a ground-up SVG UI toolkit, or even a WebGL based on if you're feeling ambitious, but giving up on the built-in browser behavior and all of the automation tooling around interacting with HTML is a non-starter for most use cases.
I love the idea of punting on HTML and writing a ground-up SVG UI toolkit, or even a WebGL based on if you're feeling ambitious, but giving up on the built-in browser behavior and all of the automation tooling around interacting with HTML is a non-starter for most use cases.