I think you are right. Catering to a common denominator while extolling past virtues is the current Celebrity. They did not need Summit and Constellation, and they may not be in a position to bring past virtues up to past levels (food, service, flair).
They were on their way to becoming a niche line, but the powers that be want expansion. I don't know about a niche line doing much of the usual, and nearby, itineraries. Celebrity probably needed to be in some areas of the U.S. and abroad that would attract those that could see its virtues. Right now they are selling a commodity with a certain style and promoting and elevating the style, while offering what appeals across the board. Bad recipe.