Re: Can someone explain.....
I realize you're not the poster I was asking for an example from, but thank you all the same for taking the time to comment.
You're right that for an old, stable system which will virtually never see upgrades or changes it doesn't make a practical difference. It may as well be an embedded system—so long as it boots, works, and is bug-free the internals don't really matter.
For whatever it's worth, I do see the value in shell scripts and have obviously written quite a few in my time. However, the poster who I was replying to specifically mentioned service files vs scripts and there's very large shortcomings with the latter approach in the context of getting the system read (at least how it's been handled historically at times). Service files are just outright better at handling dependencies and helping track points of failure in the init. What a target is wanted by, under which conditions it should run or not, user permissions, and all those little subtleties are handled in an easy-to-understand manner that's easily changed or modified according to deployment needs.
Fetching information about the state of a unit and what it's doing is also simple and there's plenty of in-built tools to analyze the information in various ways. But, I realize that we're talking about different things here. I don't have a problem with the scope of systemd being beyond basic service management and think that the upsides of more tooling and integration with other aspects of the system far outweigh the downsides. But that's a different wholly discussion than systemd being more difficult/unmanageable than shell scripts for complex setups.