I think @Wishing on a star just about nailed it.
I feel that it is not as dressy on the warmer climate cruises, such as Caribbean, Mexico etc. I’ve seen more formal attire on the European cruises for example. But, it really is a mix IMO.
Some are really dressed formally, while others are more like nice pants & shirt for the men to dressy slacks & tops for women.
Do what you want to do, it’s your vacation!
False, there is not a dress code all over the ship. Basically, the MDR’s. I have seen them turn away some that wore shorts and cutoff jeans to dinner. Some prefer to go to the buffet and they do not have to dress up.