[tom9729]

> Solved much more elegantly by the likes of daemontools and derivatives (s6, runit, etc.), many years before systemd.

Then why is no one using them?

> Hardly "new". Dependency systems in init daemons and service managers have been rolled many times, from the primitive need(8) facility to the LSB initscript headers (which almost all SysV-based distros had adopted) to OpenRC, Solaris SMF and so forth.

Exactly. Isn't the point of systemd to bring the ideas from launchd (and SMF) to Linux?