I don't think you can point at any one player and say they're the problem. The squad has many underperforming players. Even the players that the fans think aren't good enough, they have shown quality at different points here. I agree with you and think he does decent enough, but I get where people are coming from in regards to his crossing ability. He seems like very much a confidence player. You seem him go on long ball carries and easily dribble past defenders at times. Then at others, he looks like shit and can barely control the ball.
I also agree with you on Ronaldo, but it's still one of many issues.
He rarely does interviews, but in the few he has, he's a very soft spoken guy. He seems pretty introverted. I couldn't ever imagine him shouting at anybody. He's just not that type of person. Is it an issue for a United player to be kind of reserved on the field?