I think each of these address a very different problem, and completely disagree with him. Trying to bundle all of these things into one big app will just make the app bloated and development painful. Youtube at this point has many different uses (average length videos, live streams, music/audio) and trying to have a one size fits all app is not necessarily the right way to go.
Youtube GO is meant for people who live in areas with poor connectivity. Again, having them download a big 100mb bloated app is not the right solution. On the other hand, people with LTE don't care about the download size and locally sharing videos, so why put that in the same app? Same thing with trying to put Chatting/Livestream notification into the Youtube app, or trying to hack a music player into it.
