SystemD is more than just an init system, it also runs some system service, like DNS. If you still think of systemd as an init system, then your knowledge of it is outdated by at least a couple of years.
But, if you want to use it as merely an init system, feel free to disable resolved and install dnsmasq instead like in the Good Old Days.
I'd much rather have my system not working than have it randomly start sending the domain part of my browser history to Google without as much as a notification. When you install Fedora, the last thing I'd expect is that it starts acting like a tracker for Google when my DNS server goes down.
I think they should've implemented this differently, sending out a notification that the DNS configuration is broken, with the option of switching to either Google, Cloudflare or letting me fix the network configuration instead of silently failing.
The less tech savvy users are still running Windows where the exact same thing would've happened, with errors just as obscure. No matter what OS you're running, the problem is with your network config, so it should be fixed by whoever manages that instead of relying on some hard-coded defaults somewhere deep inside the DNS resolver. In most cases, that means calling your ISP or calling your IT service desk for support.
I personally hate it when software goes and does some random shit like pick its own DNS server because it somehow has determined that something was broken. Windows is full of this "smart" behaviour and it's one of the reasons I always feel like I need to anticipate its responses to my actions instead of just using it.