I agree with you that De Bruyne's entry into the team had a significant impact on the originality of Manchester City's attack. As an attacker, Haaland may find it difficult to miss De Bruyne's valuable pass. But it must be admitted that Manchester City have a history under Pep Guardiola showing their capacity to win under these circumstances. Guardiola is renowned for his ability to devise original methods and tactical mindset. He frequently compensated for the absence of key players by taking advantage of agile player rotations and effective tactical setups.
Guardiola is always trying to pick versatile players who can play in many positions and this is a very smart move as it will allow the team to rotate if necessary. But De Bruyne is more than just a good universal player, he is capable of creating scoring chances on his own and he has a great shot even from long range, the absence of such a player is always felt by the team.
KDB is one of the players who is indeed very vital for Manchester City and as you say this is not just losing a player because KDB can be said to be one of the iconic Manchester City at this time so that with the loss of him in the squad for a while this will slightly change the current Manchester City game pattern.
Indeed, it will not have too much impact because Manchester City still have a lot of options for their players but in addition, there will still be a slight difference in attack when De Bruyne is in the squad and not in the squad.