One thing that Nintendo learned in the 80s is if you want to sell a platform with a sustainable perception of quality, you take responsibility for ensuring that

One thing that Nintendo learned in the 80s is if you want to sell a platform with a sustainable perception of quality, you take responsibility for ensuring that garbage doesn't run on that platform. That means restrictions. Opening everything up on iOS/iPadOS will severely compromise Apple's ability to maintain its value-add in the marketplace as the best quality, most end-user-friendly mobile platform, as well as their security posture.