It's generally not; I've never understood the claim that either one is particularly "complicated". You either write a set of sh commands that start the service

It's generally not; I've never understood the claim that either one is particularly "complicated". You either write a set of sh commands that start the service the way you want to or a unit file that has that shell command plus some random metadata crap about it. Neither of these options are particularly difficult and I've literally never understood why people want to die on either side of this hill. The pain point was never "generating a textual representation appropriate to the init system"; the problem was always the underlying startup and teardown of the service itself.