> A technical issue is at the core of the problem (the practical inability to "just create" a new browser)
What I'm saying is that the technical difficulty in creating a new browser is less of a concern than the legal and monopolistic barriers to creating a new browser.
See your next point:
> Yes, but Firefox has to follow Chrome at whatever they decide, because the "regular consumer" just wants a working browser.
Which is a legal/monopoly problem, not a technical problem. Firefox has passed the technical hurdles it needs to pass to be competitive with Chrome. The monopolistic barriers (default bundling in Android, hobbling Google properties like Youtube on Firefox, etc) are some of the biggest things holding Mozilla back.
You can make it as easy to build a new browser as you want. But if Chrome is bundled in Android by default, and if Youtube works better on Chrome than your browser, and if your browser can't play Netflix videos because Google won't license Widevine, than all of the technical solutions you've come up with stop mattering.
The practical inability to "just create" a new browser exists, but you're not going to be able to solve that problem purely with technology.
Microsoft made a competing browser engine, from scratch, and in terms of pure performance and support for web standards it was doing really well in matchups against V8. They gave that engine up not because they didn't have the engineering chops to compete with Chrome, but because they couldn't break into the market. That's not a technical problem.