Mario Kart World's roster problem is that they seemingly decided to put an arbitrary limit on how many random npcs they're adding. If they added as many Stage Hazards/onlookers that could fit in a kart as possible and spun it as a main feature of the game like "Drive virtually anywhere, be virtually anyone!" people might be kinder to it.
It'd look less "they're doing this because of constraints" and more "they're doing this because of the creative vision"
It'd look less "they're doing this because of constraints" and more "they're doing this because of the creative vision"