I have yet to come across a situation in which it is not worth the effort to figure out how to attach a debugger to a piece of code I'm modifying.
I probably could have attached a remote debugger, and executed the relevant function a few times until my request got routed to the right process in the cluster, but that honestly would have taken me more time than just committing the print statement and letting CI take it away.
But you're right, figuring out a dev / prod discrepancy in already-running code is a case where a debugger is not as useful.