Of course you can turn it off. Fedora didn't even use resolved until 2 or 3 releases ago and they were one of the first major (non rolling) distro to adopt systemd.
Maybe nowadays, but when it came to Ubuntu back in the day it was enabled by default and couldn't be turned off because it was being used early in the boot cycle when other resolvers hadn't booted yet. Talk about bad design decisions...
Speaking of which, there are some other things that Ubuntu does that get my blood pressure up, such as not having a reliable way to do truly unattended upgrades.