The answer to small-ball actually isn't defense in the context of Rudy. It is that he HAS to impose his will on the game when he is so much bigger. He has to draw triple teams on every roll and has to be able to punish when they switch a guard on him in single coverage with aplomb.
Some of this stuff is outside of Gobert's wheelhouse, but I cannot be convinced that he can't bully a guard and just spin and dunk. We don't need immense skill, we simply need him to play his size. Gobert plays a cerebral and conservative game, but at a certain point, his mentality needs to shift into the alpha he thinks he is and just yak on fools smaller than him.