Actually, systemd keeps all of that complexity and more, it just sweeps it under the rug and makes it into a single point of failure.
Also, unless the daemon decides it wants to give up all portability and lock itself into systemd, it has to implement all of that code anyway and ignore systemd. Or worse, it can add yet another compatibility shim and accommodate systemd as well.
Of course, a SIMPLE utility could do that job on a case by case basis and be usable by systemd or sysvinit or openrc, etc etc. It could also be portable to *BSD and OSX (unlike systemd). Systemd's 'design' reminds me of Robin Williams talking about God getting incredibly stoned and creating the platypus.
As a bonus, that approach wouldn't screw up a simple thing like fstab.
Meanwhile, where are these experts and those amazing code reviews?