Another daemon for managing control groups

Uh. And what exactly stops you from using vixie cron or your own logind implementation?

The case with cgroups is a bit different, but that's not really systemd's fault - the kernel/Tejun wants to move towards a single hierarchy, not systemd. Since systemd relies on controlling the cgroup hierarchy it cannot easily use a separate cgroup controlling daemon without having pid 1 rely on other processes without similar protections as pid 1 has from the kernel.

If there's things to critize about system's cgroup handling it's that they've built an API to control cgroups in a relatively short time which they are bound to continue to provide. Since it has to be generic enough to a) be implementable by others b) not block any future cgroup usage that makes me a bit wary.