APIs are just APIs it depends on developers how they use it for their applications.Nothing is removed in a blink of an eye, developers have +6 months to test and update their Software. And a 1 to 2y heads up in feature changes as well.
Microsoft is doing well to remove outdated and unoptimized APIs.
Is not Microsoft fault the industry is lazy and refuses to envolve, they sure learned their lesson with Windows XP, those who can't stick with times get left behind.
Industry isn't lazy since you've millions of PCs with low end to high end which runs the same app on it w/o any issues and suddenly re-targetting the app to run on newer Win 10 fails to run on latest W10 but it works on older Win 10 builds which are 7-8 months old. So, when you implement a feature specific to latest version and doing that may break everything on all PCs.
6months is a small time-frame and there isn't any Long term stable Win 10 build for consumers like Linux LTS versions.