Here's a true story. I was in a CentOS 7 system via chroot and trying to troubleshoot some problems. If it were CentOS 6 I would just run "service rsyslog start" and have syslog running in the chroot so I can get the diagnostics I was expecting, but since systemd wasn't actually running I couldn't do that. I had to launch rsyslog directly by command-line, but then it didn't listen on
Systemd may be technically better than sysvinit but the latter is just shell scripts which are sufficiently independent of anything else and just work. Systemd takes over your machine and wants to get its hands into everything to the point that you can't even use it anymore without systemd. This is what we're worried about what will happen to X.Org and other software.