The correct way would be to standardise DoH and DoT and add support into it into automatic address configurations and operating systems.
Exactly. If Mozilla wants to, it's more than welcome to reach into the VPN area with its own products, but I don't believe this functionality should be part of a browser. They're already reaching into the VPN area[1], should they also investigate bypassing Chinese censorship with their own "firewall-busting" obfuscating VPN? That's not something most users want nor need in their browsers, and such functionality is really a cat-and-mouse game that I think is best left to smaller and less-well-known entities.
It's unfortunate that browsers are already beyond "neutral", when IMHO the only thing they should do is fetch exactly the page URL that was entered and display it.
Edit: yes, apparently people disagree and want Mozilla to control what the Internet (and every user, ignoring his/her default configuration) does. This is really really disturbing.