But this time, things have changed, and Manchester City may be going in for a long period of head-tight confrontation with some of the other stronger teams who may have suffered set back in the last few seasons to warrant Manchester City's success in those past seasons, but at this point, those clubs have recovered and there are really good and ready to take Manchester city head on and possibly dropping them out of the award in this season in all things being equal for those clubs.
Yes, you are right about Man City having to accept the fact that no matter how perfect their current squad is, weaknesses will always be there and will be easy targets for opponents. In the Champions League we will now be faced with unexpected competitors and Man City must be prepared with their record from last season continuing to be at stake. Bayern Munich appeared more aggressive and had an ideal squad when Harry Kane arrived, so they could be the toughest challenger to win the trophy which is Bayern Munich only dream. Indirectly, this is a challenge for Man City who feel that this season is going well but do not think that other clubs have made significant improvements to prepare for competition in the UCL competition. Becoming a stable club is not as easy as Man City imagines, because the UCL is very difficult to predict when all clubs try to show different performances in their respective domestic competitions.
I agree with this because some clubs can definitely be troublesome now even if they weren't favorites before but for the Champions League everything is unpredictable because there could be some clubs that will surprise.
Bayern, Manchester City and Madrid are still one of the favorite clubs that they are definitely possible to talk further in the Champions League but for some other clubs there could be some surprises that occur such as when in the previous 2 seasons Villarreal managed to be in the quarter-finals or indeed last season 2 Serie A clubs reached the Semi-finals so indeed all possibilities about club surprises will still occur for now.