Fresh off a notch above (allegedly) line, Celebrity, and as the ship had various plagues, nothing was self-serve. At least Carnival has more included venues, spread out, with open more hours, and less expensive room service. Celebrity does have a few uppity included venues for those who pay exorbitant amounts and higher priced specialty restaurants for the rest.
There is nothing wrong with Carnival's sea day brunch and as long as you check in before noon, you will be served. There basically is no change in hours for the workers and the differences in the menu are minuscule.