Great! And you can already choose to do so. But it seems pretty likely that Firefox will be making that decision on behalf of all its users (except those with the wherewithal to know how to opt out), without effectively communicating the risks of that decision to them (based upon their communication about this feature so far).

I host my own DNS resolver on a dedicated server, Firefox hijacking my DNS traffic without telling me is definitely not an improvement. It can be a nice feature in some situations but having it activated by default without explicit consent should be a big no-no.

I hate this mentality of "our users are complete idiots and we know what's good for them" (I call it the "Gnome" mentality).

Countries other than the US use Firefox, my ISP doesn't spy on me. Cloudflare might.

There are many public DNS providers those promise to not logs DNS queries. I don't know precisely but if Mozilla forces user to use Cloudflare DNS is the deal breaker.

False dichotomy. I.E. those are not the only 2 options.

apt-get install unbound