Unfortunately, a browser cannot realistically be controlled by a non-corporate-funded entity (if you don't count a government). Modern web browsers are incredibly complex and the web standards are made in a way that largely prevents the creation of new browsers. Firefox is mostly funded by Google, and Mozilla being the ineffective organization it is, this is unlikely to ever change.
The browser should be our user agent by default. Not some advertisement displaying, user snitching, corporate money making machine.