don't consider Princess, they don't even have a child program for kids under 3. You can go to the kids room but you must stay with your child all the time. No babysitting............ nothing
All of the major cruise lines seem to be gravitating to that policy, probably because a lot of two- to three- year-olds either are not "potty trained" or are recently "potty trained" and still prone to "accidents" with which the staff of the childrens' programs are not prepared to deal.
BTW, a major factor is that many infants now spend a lot of time in day care centers that do NOT "potty train" the children. In the past, most children were "potty trained" by age two.