Many unofficial apps for YouTube on iOS were using not allowed API from Google. It means that you could play 60 FPS videos, watch videos in 4K resolution if available, background playback, audio-only mode, which was useful while hearing music from YouTube without video to save free datas on mobile plan, and, the most important, to block ads. Now it looks like these times are over.
I was using ProTube, which I reviewed HERE. Beside official YouTube app from Google, ProTube was capable of play videos with 60 FPS and using 4K resolution, if available. No other 3rd party app on App Store could do this. Currently, the only way to enjoy these features are to use official app from Google, which is blown with ads in videos. It’s true, that you can get YouTube Red subscription, but it’s not available in all countries. Here in Slovakia, I can’t use subscription, it’s not available in my area.
Google offered to Jonas Gessner, author of ProTube, to offer his app for 10 dollars/month. He did not agree a decided to end development of ProTube. Jonas could remove key features from ProTube to keep it alive at App Store, but it would make from ProTube another commom app, as many others on App Store.
It’s true that you can keep ProTube in your iTunes library, but in future may happens that iOS update will break ProTube and no update will be available.
It’s interresting, that ProTube was on App Store for very long time without action from Google. In past, you were able to download videos via ProTube, but this feature was soon removed.
Another category is Picture-In-Picture, which was brought on iPads with iOS 9. In this mode does not work ads from Google, so it’s possible, that this feature may be removed from many 3rd party YouTube apps on App Store. As expected, this feature is not present in official app.
Full statement from Jonas Gessner is avialable on his website.