Well, Kevin De Bruyne is a very important player in the midfield for Manchester City. It is nearly impossible to actually find a player like that. So of course when he is not there, Manchester City is going to find it really hard to manoeuvered the ball in the midfield area.
Does that mean Manchester City is useless right now? No absolutely not. But the freedom and authority that Manchester City had over the midfield in almost every match is not there right now without him. And without him, the supply for the forwards are also not going to be amazing, to be honest.
Manchester City was having struggles winning games. Reciting the problem to the absence of Kelvin De Bruyne is absolutely out of line because I could remember really good that Manchester City have won important games this season without his presence on the pitch, why tender blames for absent of key players this very moment when they have starts to face setbacks in league games? It's necessary and important how they cope and play a better pattern of football all these past months without Kelvin De Bruyne, why complain now that they've experienced slight struggles in league games?