This. Nintendo wanted a land built for the family, because they make games for the family. Mario Kart was never going to be a Hagrid-sized thrill ride. Hell Uni initially sold Hagrid as a "family" attraction, and it's definitely not.
Another thing to remember is a ride like Indiana Jones Adventure goes like 15 mph, tops. That's still a pretty dang thrilling ride. The visuals and some clever tricks will make Mario Kart exciting. People here are acting like it's gonna be Little Mermaid or something.