Apple should take some responsibility for this.
Although it was Google's decision to deprecate the older YouTube API I am sure they gave everybody lots of time to update their applications.
Apple and Apple alone made the decision not to support the updated YouTube API on their older devices.
I remember being very frustrated when Apple phased out the Apple TV 1 but was able to console myself with the new features which for me were mainly the Netflix app.
I see no reason to buy an Apple TV 3 just to get back the functionality I believe I paid for....
So I have purchased an Amazon Fire TV which will get me back on YouTube with the addition functionality of Amazon Prime Video.