NewPipe is a lightweight youtube frontend for android. It's supposed to be used without the youtube-api and without any google play services. NewPipe only parses the youtube website in order to gain the information it needs.
This a very early version of the app, so not all functionality is implemented, and there may still be a lot of bugs. But all in all it's doing what it is supposed to do. It makes it possible to watch youtube videos. So don't be cruel to this app. It will improve...