Grizzly, I totally understand your point about wanting to experience the "Super Mario world" rather than a "Super Mario racetrack." And I actually agree with you. Being able to finally feel the experience the feeling of LIVING inside this world is what makes this idea so special to being with.
But think about it this way....that feeling of being inside the Super Mario World can be experienced on a Diagon Alley type walk-through street. And it will be so much better than experiencing it through a ride, because you can take your time and soak up every moment, every little nook and cranny. Imagine being able to walk inside Princess Peach's castle with the paintings, being able to climb on warp pipes outside, mingling with Toads, and jumping to break open QUESTION MARK blocks....all while hearing the famous Mario themed music playing in the background. It will be magic.
You'll still get that feeling of finally being able to inhabit this world. Nintendo will make sure of it. Having MarioKart as an actual ride on top of that is just icing on the cake.