for most cruise passengers, it is a new show. the majority of cruisers on any ship at any given time are first time cruisers. It would be the same on any cruise line.
I also think that is partly why the cruise line gives discounts for past guest.
even tho they are the same, I still enjoy them. I have done 10 on carnival, so I have seen them several times. and enjoy them every time.
I also think you may be a little harsh on carnival.