It's when i meet against some awful design choices in systemd, like how it decides to wait forever rather than hard fail, and by wait forever, i mean wait for 30 seconds, no, 1 minute 30 seconds, no 5 minutes... you get it.
Or you can easily lock yourself out when there's a typo in /etc/fstab.
Or the hardcoded 5 minute timeout for sysv-generator: https://github.com/systemd/systemd/blob/main/src/sysv-genera...
God forbid you used cgroupsv1 for anything when poettering unilaterally decided to punish everyone with a 30 second delay for using it.
If you stray off of the intended opinionated path, be prepared for the least user-friendly experience linux has to offer. You might even get some abuse from the developers if you try to ask for help, but they've probably toned it down since CoC became a thing (I hope).