Can you define spaghetti in this context, and point to examples in the code?

Yes, systemd is far from trivial. The model of its operation is rather convoluted.

But most people just don't care. long running applications are wrapped in a control group, can be reliably killed, stopped, etc.

There some questions around binary logs, yes, but nothing truly unbearable.

Which is the proper place for complexity to live in and get properly tested by millions of boots each minute. Remember, essential complexity of a task can never be reduced.

As opposed to that shitty bash script you pasted from 3 stackoverflow answers that already has 3 bugs just from existing, let alone all the indeterminacy that comes with it execution with all the other similarly shitty bash scripts, all unique to your system.