I would be curious to know how true this has been during the lifespan of the parks and when/if it changed. My memory is that one of the issues with the Disney brand generally that was identified when Eisner took over is that it appealed to people when they were children, lost them when they became teenagers, and only regained them when they had children of their own. This was part of the logic for diversifying the options available at WDW and, on the studio side, creating Touchstone.
Unless I am misremembering something, then, I would be interested to know when Disney transitioned to a point where they held customers throughout their life and then when that changed and what made it change. I wouldn't think it would be pricing so much, as that is more pricing certain consumers out entirely rather than, say, making the parks less appealing to teenagers. As a brand, I would suggest that Disney is actually more all-ages now than it has ever been.
I don't know if age appeal has changed much, but the post Baby Boomer and generations that did not have Davy Crockett to Cars are certainly spending less or moving on in numbers. There is more competition than ever.
The branding gap is much different and thinner than ever before.
Thing are reasonating very differently and Disney theme parks have been a mature project for a long time. There is naturally a bit of a decline before/if the cycle continues back.