Earlier quoted context omitted.
Wasn’t Netscape the case study of why you shouldn’t do a full rewrite?
AFAIK Firefox is not doing a full rewrite but incremental refactoring then attempting to swap components. The unfortunate truth is that writing a browser is almost impossible because of the complexity, IMO we need a new version of the web that breaks compatibility, make everything strict(no longer ignore errors and guess a fix for them) no more 12 ways to center an element , for the legacy web we can use the existing…
Here's an example of website written with Rust and rendering all UI to canvas: https://makepad.github.io/makepad/ it works right now and it's very fast and smooth.
IMO tech for next generation web apps is already here and it's great.