It would be significantly worse, unless there is a very good reason for that (e.g. some app like Photoshop could work that way).

You lose any form of accessibility, inspectability, AdBlocking won't work, in many cases even mouse select/copy-paste won't work..

I didn't say it'd be better. Just it would be simpler.

No need to learn html, css, JavaScript, bundlers, etc, etc.

You will inadvertently reinvent the browser inside a browser but worse.

Nah. There's so much stuff that would need to be implemented.

Just think of all the functionality related to text that browsers give you in HTML: styles, spellchecking, accessibility features, etc. And that's just text.

Most people would just use the most popular framework that did all that for them, while the remainder would complain loudly about the shortcomings of that framework, and we’d be right back where we started.