Too many players are not good enough.
Kevin de Bruyne and Riyad Mahrez both scored twice, with Jadon Sancho also scoring for United.
Phil Foden hit the post with one of their many chances, and United were completely outclassed, only forcing Ederson into one save.
The former United and City goalkeeper was watching the game on Radio 5 Live and said that he thought the half-time break should have changed things. The second half was worse than the first. At no point were United in the game.
Far too many players are either not good enough or don't care. He cannot do much because he has an interim manager. He knows he won't be there, so what can he do?
Manchester City were majestic, but they haven't had to work that hard for it and I think that will hurt United most.
Roy and Gary went further on Sky Sports.
In a derby, United gave up and it is unforgivable.
I can forgive mistakes, but not running back, not trying to tackle, and there are players out there who shouldn't play for Manchester United again.
We have all lost football matches but it is the way they lost. They are expected to play with a bit of pride but that is a reflection of where the team is at the moment.
If you can't run back and put your body on the line when you're playing for Manchester United, it's shameful.
He accused Fred of looking like he was waiting for a bus instead of trying to get the ball.
Who is running that dressing room? How am I looking? these guys seem more bothered about that. How is my hair looking? Is my boots nice? When you play for United, you leave your ego at the door.
The Red Devils are outside of the top two in the league because they didn't have a chance in the second half.
The final 25 minutes of the game were described by Neville as a disgrace.
He said that after the third goal, City had 98% possession.
The dressing room isn't broken, but it isn't far off. When the going gets tough and a lot of them go missing, you find out what it is like.
Chris said that United were embarrassed by their city rivals.
In his 18 games in interim charge, Rangnick has only won eight of them, with a permanent successor likely to be named this summer.
It is a difficult game that shows we have a long way to go.
Everyone knows how good the City is. They are one of the top teams in the world and there is a gap between them.
Jamie Redknapp, an ex-Reds player, suggested that his old side would be angry with what he saw as United's lack of fight.
Manchester City created a team and thought about their players. United threw money at the team and hoped to find a team. He said that it was not working.
It takes time and it takes the right culture, but at the moment United are a million miles off. I would be angry if he was watching that.
United didn't even try. There was no structure or idea.
The second half was one of the highest levels we have played at in a long time.
I know what it means to our fans to win the derby. We should have scored more goals.
He admitted that United had caused problems for his team.
He said that it was so aggressive that it could be done without the help ofRonaldo. It was difficult to make it up. The counter attack was more successful in the first half.
The movement from everyone was excellent and we played really well in the second. The decision making during the game was good and that was the reason why we won the game.
The man who scored two times told the BBC: "We totally controlled the second half." It is hard to take us when we are like that. We have confidence in our football, but we are taking it game by game.