Parents and children can have fun together on a playground.
Who goes to Disney? Families with kids where the parents grew up going to Disney. Families with kids who have never been to Disney and would like to go so everyone can have a good time. Adults who were kids that grew up with Disney.
I don't have the numbers, but I highly doubt there is a sizable portion of Disney visitors who are just adults who never went as kids and have no prior attachment to the parks.
I'm not knocking adults who enjoy Disney World or theme parks in general. But the main goal of the parks is to appeal to children or the child inside us adults.
@UNCgolf said it's a bad idea to gear entire lands towards children. Fantasyland? Toy Story Land? Mickey's Toontown? Dr. Seussland? Super Nintendo World?