In my opinion.... I think things are just different today. I think kids are exposed to so many different ideas and experiences just through social media/internet alone that going to Disney won't get the same kind of passion.
For me, WDW was a place that I saw the future of living underwater (in all of it's 70's glory), magic happened, characters were alive, I walked through pirate towns, flew on a pirate ship and stayed in hotel that seemed like Hawaii.
Today kids have so many outlets for their imagination that we didn't have. They are often well traveled at young ages. Heck, they have Universal/IOA - Harry Potter! We didn't have any other parks like Disney at the time.
I'm not saying they won't love Disney and like to visit, but it's hard to imagine them having the passion that Horizons gave to me when I was 10.
Now everyone go ahead and yell. I'm just the worst!