Earlier quoted context omitted.
What problems do you have with the official app? I normally have large list of complaints about video streaming services, and I don't have a single issue with the Android Youtube app
My big issue is the backgrounding. I like watching a video while cooking, but I also need to use timers. Not having the video stop and re-orient itself to portrait while I quickly set or dismiss a timer is excellent. I also find the UI during live streams to be borderline unusable on mobile.
Background playback is a paid feature. You may disagree with that decision but the option is there if you wanted it.