I think one of Manchester City's mistakes this season is that they let Alvarez go, so when Haaland is not at his best there is no player who can replace his role. Usually Alvarez can be a player who can complement Haaland's role in the front line when Haaland is not playing at his best. Regarding Manchester United, they are a team that cannot promise at all and I even say they are very lucky to get points in this match. They have lost their identity that they once had in the past, who knows how long the decline they are experiencing will continue.
At big clubs, mistake like this can be made because the head coach can not give too many opportunities to young players who are not patient enough for waiting given chances. In this season Manchester City made a big mistake with Julian Alvarez, and in the past season they did the same with Cole Palmer. Chelsea years ago made mistakes with Lukaku and Mohamed Salah, and you can find more similar examples.
Manchester City tried to support Haaland with Marmoush from winter transfer season and this striker generally played well, not only at his favorite striker position. However he is a new comer in the club and needs more time to absorb tactical philosophy of Pep Guardiola and combine better and more smoothly with his new teammates.
Yes, I can understand that, because it is impossible if they knew what would happen in the future, they would do something that would harm them. But they did not know that something like this would happen, on the other hand, players must also have their own desires if their position in a team is not the main one, they must look for a team that can give them the main place. But actually I also suspected this, even though they have been able to defend the title for 4 consecutive seasons, it is impossible for them to always be able to do that. Moreover, this is the English League and I even considered it extraordinary because it is not easy to defend the title for 4 consecutive seasons in the English League.