Although it is possible to write everything, right up to the view model (but not the view) in something cross platform and performant, keeping the GUI/view using only those languages/frameworks which result in native feel (both in terms of look and performance).
Sure, writing the GUI properly for each platform still requires more work, but far far less if all but the front end is cross platform.
However, it very rarely seems to be done, even with modern additions and improvements in C++.
