Even with Rocket League microtransactions are a bad idea. It incentivizes the developer to make attaining items through gameplay a slog in order to get you to skip that by paying up. If there was no way to get those items through mtx, they'd make the process of getting them fun.

Also, games are supposed to be a form of escapism, where the gameplay matters, not who you are and how much money your parents make.

You can argue in favor of the game itself being free allowing people to save 10 or 20 bucks. But gameplaywise Microtransactions inevitably make the gameplay experience worse, without exceptions.