[viraptor]

> cgroups? Other managers exist.

For resource quotas? Cgroups is a kernel interface. What kind of manager do you have in mind?

> daemon/process management? daemontools, runnit, s6, etc.

None of them can deal with runaway daemons. Some of them can deal with ordering and pre/post conditions and instancing, but not as extensively. Each provides a different subset of systemd's init features.

> Running/waking a program from network activity? inetd (xinetd) has been doing that since the '70s.

Inetd works in entirely different way. Those approaches are not comparable at all. (Systemd can hand off the whole listening socket)