connecting Apple TV app and other streaming services?

The Apple TV app supports other apps on the Apple TV set-top box and iOS mobile devices.

Availability of supported apps in the Apple TV app - Apple Support

The Apple TV app does not support other apps on the Mac or on third party streaming devices.

It does, and notes that not all features will be available on all streaming devices. On Mac, it does not have other apps available and on other platforms it cannot communicate with other apps. Hence, it is not able to initiate playback through other methods and relies exclusively on what is available directly within the app (iTunes purchases/rentals, Apple TV Channels)