I disagree. Compare macOS today with the initial OS X release and it is fundamentally the same system both UI wise and code wise. Windows and even Linux has see

I disagree. Compare macOS today with the initial OS X release and it is fundamentally the same system both UI wise and code wise. Windows and even Linux has seen far more dramatic UI shifts in the same period. Same goes with the code. Windows went from win32 C API to C++ API with MFC and ATL. Then they promoted COM and Visual Basic development. Only to change gears and make C# with a completely different API. Then winforms gets depricated. We get silverlight, WPF and then there has even been more stuff in later years and I lose track. Compare this to macOS which ever since OSX has used almost exclusively objective-c and cocoa. Even now with swift you can use cocoa, and pretty much all apple technologies you allready knew. C# made redundant all previous win32 and VB skills. The introduction of Java, python, ruby and Go have not let you use any previous skills or libraries. In this regard Swift is an amazing accomplishment as you can reuse so much existing skills and code.