I think another issue is that on Apple's platforms the changes are quite abrupt, whereas most other platforms are gradual. E.g., if you wrote a Qt (the toolkit) application in 1996, you could have slowly transitioned your application to Qt 5 version by version. In the meanwhile, you have gone from non-standardized C++ to C++98, to C++11. So, you would have an application with a modern language and toolkit, which was gradually developed over the last 23 years. The same for Windows applications.

For me, the truth is somewhere in the middle. Yes, there is more churn on Apple platforms. On the other hand, it also allows Apple and the ecosystem to move faster. It is amazing what they have been able to achieve with (just naming some random things): wide Touch ID support, Metal, or application sandboxing.