I have also found that when complaining, be it cruise related or anything else, to state that I am aware that it is not the fault of the individual to whom I am speaking. Unless of course it is. But, usually, the poor person did not create the problem, but has to deal with all complaints. Recognizing that often makes them more willing to try and help. And, if not, at least maybe I took a tiny bit of stress out of their day.
I will never forget the cruise where the wealthy, arrogant gent at our table happened to be in front of me at the pursers' desk when we were at sea to avoid a hurricane. He actually tried to blame it on the person manning the desk. I spoke up to remind him that a hurricane is legally referred to as an "act of God" for a good reason!