I don't understand how the concept of a run button dumbs it down, though. I have never played a single Mario game where I ever felt the need to walk, so naturally I just kept my finger on the run button while playing 3D Land and the classic games. The lack of complex jumping mechanics and more than 16 specific directions you can run, sure, that sucks, but having a run button simple makes things more precise.
Also, I'd just like to say that while 64's controls were amazing for just fucking around and enjoying the game, they really are rather poor by today's standards of precision platforming, Sunshine and Galaxy improved upon them 100%.