Just to add on to these points, because they are 100 percent true. Disneyland Resort (and all other resorts up to date) were built with Disney's vision of 1) getting away from the outside world and not having your everyday struggles and worries ruin your day. 2) Also taking guests and putting THEM in the story as heroes or navigators, or even tourists traveling through a very foreign environment (i.e. Jungle Cruise, Indiana Jones, Pirates of the Carribean, and so on...) and 3) the premise behind the park was that Walt wanted to be able to ride attractions with his youngsters or have his youngsters ride with them to share in the enjoyment and experience.
That is part of Disney's formula, the family experience. To enter through the gates, and lose yourselves as a family in Adventure, Fantasy, or in Tomorrow. Yeah California Screamin' is a great coaster to teens, enthusiasts and other young adults that enjoy riding rides, but the kids have to be left behind (i.e. 48 Inch height Requirement, too scared/intimidated). Yeah Flik's Fun Fair is enjoyable for the little ones, but seriously, what adult wants to ride the lady bugs when in the other park you have the Mad Hatter Tea Party (Tea-Cups) where you can ride with your child in a much more enjoyable environment.
I by no means am a DLR Fan-Boy. Yeah I love Disney but I thought I would finally post this because I think a lot of people miss the point when everyone else is talking about why DCA has not been a popular destination for over 10 years.
EDIT: And for the record, I enjoy Thunder Mountain any day, any time... Probably nostalgia for me but whatever right?