Of course, I've run into people who don't like WDW, and I've recently gone there with people who don't get it, and there are generally a few catagories people fall into.
1. They went and tried to do everything in less time than is really needed. Of course, they did not have fun.
2. They went during the height of summer or during other "school's out" times and did not have fun due to the crowds. Many teachers fall into this category.
3. They are thrill-lovers who do not appreciate dark rides or shows of any kind. I went to WDW last week with a fellow that could not understand why I liked Imagination, Pirates, or Buzz Lightyear. "There's nothing to most of these rides but blacklights and flourescent paint!" he would cry. He doesn't get it anymore. He had not been in several years and said "I remember liking it more than I do now". Folks like that "grow up" and just can't appreciate it for the artistry.
4. Those who hate to be educated or refuse to watch educational programming usually dislike WDW, especially Epcot and AK. I know several people who despise Epcot, but my family and I love it. We also love watching Discovery Channel, too.
5. Finally, some people hate WDW because either they can't afford to go or refuse to pay what it costs to go. These folks will come up with all kinds of excuses, complaints, and comparisons to make themselves feel better about not going. It's only human nature. "We can really only afford to go to Six Flags, son." "That's okay, Disney World sux anyways!"
I've had the same problem as far as kiddy-ness is concerned. Besides WDW, I also love Nintendo games. Nintendo generally makes games that are "family-friendly" (sound familiar?). Many gamers can not understand why I would want to play wholesome games with bright, colorful graphics. "That stuff's for kids!" they say. Yes, like WDW, it is designed to be accessible to kids, but it's also designed to be challenging and enjoyable to everyone who can appreciate it.