It is very sad that De Bruyne was only able to complete 1 match in the League this season and had to be replaced due to injury. I can say that currently there is no player who can play a role as good as De Bruyne as a tempo maker for City's game in the middle of the field. Even though you have a striker like a goal machine like Haaland, without sufficient ball distribution it will be difficult for Haaland to repeat his extraordinary performance last season.
When a player who is often relied on by the team is injured and has to be absent for a long period, of course this will have a big impact on the appearance and performance of a team like Manchester City. So this is also normal because substitute players are always not the same as the players the team often relies on in certain lines and even attacking players like Haaland can't do much when one of the mainstay players is absent.
As you said, his teammates are fine but the problem is that the 2 defeats City have suffered at the start of the season will slightly hinder their chances of winning the title. I'm not saying City can't win the League, it's just that this time it won't be as smooth as the previous season.
Manchester City still deserves to be considered as a team that is in the category of fighting for the title again this season, but with the two defeats that Manchester City has experienced, of course this will be an obstacle for him if the rival team can continue to win consistently until the end of the season. However, over time we also need to see how the match results are obtained by rival teams this season so that Manchester City's chances of winning the title again this season can be seen more clearly.