We stopped cruising with Carnival due to the cabin temps. The last several cruises we took our cabin was like a sauna, we literally went up to the serenity deck in the middle of the night to sleep. Guest services would send someone to check the temp they would point the thermometer directly at the vent and say it's within range. Range is 76° to 78°.
I don't know about most people, but that isn't acceptable to us. When you've been in the sun all day, I want to return to a cool room.