It's an okay game when compared exclusively to other F2P mobile games with similar gambling and microtransaction economies, but outside of that I cannot agree in the slightest. It's really, really bad.

Even outside of the predatory economy it is constantly begging the player to buy into, it relies on a gameplay loop that accentuates the worst elements of Mario Kart, asking the player to do the same course over and over again until they get lucky enough to get multiple frenzies, not get hit by an errant Blue Shell or Lightning, and stay in the lead throughout to get a high score. And that's if the player has characters in the top shelf and leveled enough to make a high score attainable WITH best case scenario luck! The game's automatic acceleration and course correction is strong enough that it diminishes how much winning is based on skill, making multi-player more based on random luck as well, to say nothing of when the items are set to default and the randomness is skewed significantly in certain players' favor.

If you're willing to largely ignore the game's score gameplay, it has the solid Mario Kart core that is fairly fun. But that's a huge "if", since that is what all progression is based on. Well, that and spending money.