Now that you mention it, I find systemd messing with my DNS settings incredibly annoying as well, so I can’t help but agree on that point. At this production system at work, when troubleshooting, I often need to alter DNS between local, local (in chroot), some other server in the same cluster, and a public one. This is done across several service restarts and the occasional reboot. Not being able to trust that resolv.conf remains as I left it is frustrating.
On the newest version of our production image, systemd-resolvd is disabled.