We agree. It's just that if we try to see what Pep planned and did, there were changes made when De Bruyne suffered a long injury. Several times I tried to examine what Pep did with his team, as well as the system he implemented. In fact, based on my personal point of view, Pep is trying to make several rotations and look for the best composition with the ideal pattern for the available players. In the end, in several matches, Pep implemented his 3-2-4-1 pattern again. Even though his team did not play optimally, they still played well and won the match, especially against Leipzig on the second matchday of the Champions League.

The problem is different when City meets a tougher team, as proven against Arsenal, Pep chose to apply the same 4-3-3 pattern. that means, I assume that even though City continued to play the match well, the needs and performance of the team's squad were not completely what he expected. therefore, Guardiola tried several times to rotate his players. In fact, Grealish is often left on the bench. However, I think the coach is preparing something else for his team due to several players leaving and De Bruyne's injury. Well, we'll see what happens next.
On Matchday three, their opponents will be Young Boys. Most likely, Guardiola will rotate some of his players again.
By the way, so far City have not experienced any problems in this competition and I remain confident that they will continue to play their best in this competition.