A 'replacement' for systemd should be designed to be drop-in: /sbin/init should read unit files (which in general are much nicer than init scripts), should provide systemctl with the same options, and if dbus is also undesirable (which most people who burn with fire-y rage for systemd do), should replace the communication between processes like systemctl and /sbin/init with something else, like a Fuse or 9p filesystem.

That would be pretty neat. But until then, the world will continue to run on systemd, because it _works_.