I've run across a couple of cases where the "depends on" part seems to intermittently fail. That is, the implementation seems to end up with a race. That presumably means that the dependencies were specified incorrectly, but getting it right seems to be quite difficult. Or, conceivably, it's a bug in systemd, but debugging that is a lot harder than debugging a couple of tiny shell scripts.

I'm not necessarily a "remainer" on the subject of systemd, but I think it's not correct to sell it as a huge win on simplicity. Maybe it is simple when everything goes right. When it doesn't, though, systemd is fairly nasty to deal with.