It's a struggle, isn't it?
I get the same questions. Coworkers, parents, friends.
My reply is always that if you think Disney is just for kids, you're doing it wrong.
I hated Epcot as a kid. Didn't get it. Didn't get the point of it. Didn't get how anyone could consider that fun. Seemed like an incredibly boring place. And this was back when Body Wars, Cranium Command, Imagination, etc were all open and Captain EO was impressive. HA. Now Epcot is definitely one of my favorite parks. That park is an adult park.
Hollywood Studios is also, for the most part, and adult park. My wife goes there mostly to shop.
DTD is a place to shop and grab margaritas for a calm night out.
None of those three things were considered "a good way to spend a vacation" when I was a kid.
Magic Kingdom is a family park, not a kid park. Main Street is fun for all ages. Fantasyland is for the most part geared towards children, but Be Our Guest is one of my favorite restaurants ever. Plus, find an adult that doesn't find some nostalgia in the world of Disney. There is fun to be had for all ages in every land in Magic Kingdom. Walt really did succeed in his plan to build a theme park where everyone could have fun.
Animal Kingdom is basically a zoo. Zoos are for everyone. Kids don't appreciate the worlds Disney creates as much as adults either.
Disney takes you to a different place. That means something different to adults than kids. For kids, it's going to have fun. For adults, it's getting away. Kids don't worry about the projects they have going at work, the mortgage payment, the bills, the drama (unless they are teenagers). They don't need to get away from anything. They're just going to a more fun place. I have a real issue unwinding from work. It's a family business, so when I'm gone, I'm not necessarily off work or not thinking about it. Disney is one of the few places that force me to forget. Stand on Main Street watching Wishes and think about work. Not possible.
Another thing I say about Disney is that you don't have to drive. Maybe you drive there, maybe you fly and take the magical express, but once you arrive at your resort, put the keys in the safe for a week. It's a great feeling, especially for those of us that drive for a living. When the key goes in the ignition, I feel like I'm working. For a week or so, I get to sit back and let someone else do the work. When we go have some drinks, we don't have to worry about a DD.