Firefox

I agree it's much less egregious than the other examples in case of Librewolf, but I don't like the dependency on Mozilla addon servers by default. Mozilla has already shown themselves to be bad actors, and I'm not totally trusting of their repositories, even if ublock or whomever else has done nothing wrong. If it wants to fetch extensions by default, I would at the very least hope they incorporate some sort of checksum verification against an extension compiled/copied from ublock's source.

There's also the problem of extensions auto-updating, which is problematic for security for hopefully obvious reasons.

Librewolf is the arguably best privacy browser. You haven’t named anything better.

I named qutebrowser in my first post. Privacy and security can (and should) come from outside of the browser, through system-wide dns blocking and firewalling (torsocks if you need tor). Inside the browser, there's domain-specific script toggling, as well as userscripts. If a user decides to use 3rd party firefox extensions, that's up to them; but I don't think it should be a default.