iOS and Android mitigate some of the problems by cutting off backwards compatibility at some point. "Yeah, your app broke in the new iOS/Android ... fix it". Python's tried some of that, but because people can carry on supporting/using Python 2, the result has been a crippling fork.

Linux kernel devs spend a lot of energy trying to maintain compatibility with warts, and still break things once in a while. Also the Linux kernel interface, while complex, is nowhere near as complex as the platform-level API for iOS/Android/Web.