The part-time job you complain about is somebody else’s dream shift. Complain less, show up better.

A job can be genuinely tedious and also be the thing somebody else is waiting by the phone for. Both are true at once and neither cancels the other. The complaint is allowed. The hours are still real hours that somebody handed to you, which is worth remembering on the shift where nothing goes right.

Keep the complaining for people who signed up to hear it, then go and be good at the job anyway. Learn one part of it properly. You are spending the hours either way, so you may as well get something back.