This is according to messages that users are seeing when they launch the app on their Apple TV. It reads, “Starting early March, the YouTube app will no longer be available on Apple TV (3rd generation). You can still watch YouTube on Apple TV 4K, Apple TV HD, iPhone, or iPad. With AirPlay, you can also stream YouTube from your iOS device directly to any Apple TV (3rd generation or later).”
It is unclear why the app will stop working on the third-gen version of the Apple TV, but if you do watch YouTube a lot from it, then maybe it’s time to upgrade. Either that, or you can always use AirPlay to stream content from your device to your Apple TV. However, there are plenty of reasons to make the upgrade.
For starters, the newer Apple TV remote makes it pretty good for gaming. Also, the support for 4K content is also a very much welcome upgrade, especially if you own a 4K compatible TV, you might as well take advantage of it, right?