And even if you could do it, it's not a given that you can make a good one.

In fact, I believe making a good browser is impossible because the web is fundamentally broken. The standards require your browser to be crap. The browser is no longer a user agent, it's a server agent, and trying to block & work around antifeatures is akin to writing an antivirus program that somehow detects and blocks malicious code without breaking the rest of the program. You can try, but it's a ridiculous never-ending cat and mouse game and if you don't keep up, you just end up "breaking the web" without actually making any part of it good.

I know the code that I and my team contributed to Mozilla was only some trivial part of the whole beast, but for us it was drawn from years of work.

And that’s the whole point.

Mozilla has made a browser. So has google. Why make them out to be bad actors for providing something that is too big for mortals to even contemplate?