that and cron always felt fragile too with a lot of quirks and limitations you had to work around instead of being a robust thing from the start.
But that's because I'm old because obviously systemd-* is the only right way and everyone else who see things differently is a pundit.
I have done scheme all my life, which is why I prefer shepherd. Not only is it in a syntax that i can use elsewhere, I get completion in Emacs.