Pep Guardiola will never regret for his decision to release some players in this summer, because his plan always bring good result at the end of the tournament, which I know that the players that left will not affect the Manchester city performance in this season. I don't think the coach will disappoint his fans in this season because Erling Haaland and other strikers are still there to make things happen in this season like last season that made them to embraced UEFA champions league title and premier league title. Based on the way other teams are bringing in new players in this season showed that they will make this season tough for Manchester city, but I still have confidence that Pep Guardiola will still help the team to win the title.
Pep Guardiola is a manager who is quite good at assessing players, so agree with you that the departure of some of their core players who have successfully brought Manchester City to win the Champions League will not really affect the team's performance, maybe there will be adaptations for their new players but so far the players Manchester City have bought have always adapted well and when it is seen that they have not developed much there are players from the bench who are quite capable of covering that.
Some of the players who left Manchester City were old enough, so maybe they let these players go because as a routine form of squad renewal so that their team is always filled with young players so they can always compete well in every season.
Erling Haaland will be the foundation for Manchester City on the front lines, and this player is reportedly quite disciplined in training and keeping his body fit so City need not worry that he will experience a decline, especially at a very young age he will develop very well at City.