I agree with you about the pasenger space ratio. I have only been on larger ships and I have found no waits. Not at embarkation, disembarkation, at buffets, at the pursers office, at bars, no where. To me I like more people and I love how much there is to do on the "mega" ships. From the rock climbing wall, to ice skating, to full size basketball courts, and plenty more. Also more families are on the bigger ships, partially from the length on the cruise and it has more that attracts the families. Such as a skating rink or flowrider. plus on the bigger ships they have more room to expand and grow with ideas and add new ones.
And on the big ships it doesn't feel crowded and I never see 3500 people. The most I see is in the dining room or theater and it's supposed to be that way.