It's very difficult and sad to see Man United's football game for a few years. I followed Ronaldo's debut at Man United if Scholes, Flecter, Vidic and Ferdinand still play, it was very different. The flow of the ball and their fighting power was fantastic. Today Man United look weak, even the flow of possession looks bad. Even today Man United lose to Man City for game.
Ronaldo is not maximal because he doesn't get the ball well, even I see he has to help defend. The connections between Man United's current players still don't look solid, so they often rush and make unnecessary mistakes.
It's not all responsibility of Ronaldo. He joined them since the summer and their issues are not new and not only exist in this season. Ronaldo came and brought more goals for Manchester United but he makes their defense ability down because he does not try to hunt for ball like other players.
So with Ronaldo in a team, you must provide him good passes, more balls and he might score goals for you. However, the disadvantage is you will have to allocate more tasks for other players to fight against counter attack of opponent. Ronaldo is useless in this task. His appearance probably bring conflicts and break down a whole team. However, if other players fail to play together, and connect with each other, it is not all belong to Ronaldo effect.