Adult Park Goers - I know this may go against many, but to me the parks are about the kids....always has been and should be IMO. My wife and I weren't shocked that people would be there without kids....just at the large number of people that were....and I'll just leave it at that.
I think you will have trouble finding anyone else who agrees with this. I actually have often thought the opposite. WDW IMO is a vacation destination. Most of which is not for little kids. Disneyland would be closer to something that is more for kids.
I actually feel the opposite. I can't imagine myself taking a 2 year old to WDW with all the crowds and chaos. Kids would have to be at least about 7 or so before I would plan a trip for them. Not expecting anyone to agree with that, but I've often thought this when I see tired cranky toddlers throwing a tantrum.
Anyway, those adults paid their money and have just as much right to enjoy all that WDW has to offer.