we want a casual sophisticated cruise
With this criteria I wouldn't think Celebrity would fit the bill either. Somewhat sophisticated.. yes, casual... not really.
To meet your criteria, you may want to look at Oceania cruises, or one of Radisson Seven Seas select "casual" cruises.
I've been on quite a number of Carnival cruises (as well as Celebrity, Princess etc) and I've honestly really never encountered more of the problems you mentioned on Carnival as I have the other lines.
Every sailing of every ship on all the major cruise lines can have different sorts of crowds.