The Mario Kart Tour game will be updated around July 2022.
Along with the update, the supported iOS versions will be updated to iOS 11 or later.
Note: If you are using a device that is earlier than iOS 11, you will no longer be able to play Mario Kart Tour on that device. Please update your OS to continue playing.
To check your device's OS version, go to Settings, General, About, and check Version or Software Version.