Re: I wonder what the excuse will be this time.
I searched and discovered that per its authors: "[i]n contrast to the glibc internal resolver systemd-resolved is aware of multi-homed system, and keeps DNS server and caches separate and per-interface". So the justification for a new resolver was machines with multiple active interfaces, that possibly go to different networks.
The justification for bundling that new resolver with the init system? No idea. For distributions switching to it despite it not functioning very well? Clueless.