Most people: The open world in Mario Kart world is mostly empty open world
Fanboys or People whit buyers remorse: OMG its not empty at all you jut need to drive slow and loot at things in the environment the world is not empty if you drive to look at things not everything has to be game-play.

Iv gotten this exact response from people who diehard defend FFXIV open worlds that literally only exist as set dressing for story the shittiest sideqests ever imagined in a video game to farm fates in and occasionally hunt trains.