Earlier quoted context omitted.
Mantle still doesn't solve input, audio, and a number of other services that DirectX provides in a unified way. Also, potentially AMD only, which has a smaller share than both Intel and nVidia.
All those other DirectX parts have been deprecated for a long time now. The only thing still being used is Direct3D.
Not true. Many deprecated components were replaced with other components that are part of the DirectX package and are still used.
DirectSound -> XAudio/XACT
DirectInput -> XInput
Etc.