https://www.macrumors.com/2015/04/20/youtube-older-apple-tv-discontinued/
Bummer...this might be the year I finally upgrade the aging Apple TV 2.
YouTube today announced changes to its YouTube Data API, causing many older apps on various devices to stop functioning. On the second-generation Apple TV or older, the YouTube channel will no longer be accessible, and on the iPhone, iPad, and iPod touch, iOS 7 or later is required for the YouTube app to function.
Second-generation Apple TV users will have no way to watch YouTube videos on their devices after today, but iOS device owners with versions of iOS older than iOS 7 can use mobile YouTube in Safari to watch videos. YouTube is sharing the news via a discontinuation video that's being shared on all older devices.
Bummer...this might be the year I finally upgrade the aging Apple TV 2.