As long as the players substituting the departing ones are of the same league and they can find themselves harmonizing well with the team then it is only natural for Guardiola to not be concerned.It is very difficult to win the UEFA Champions League twice in a row so even for a team like Manchester City who could easily beat anyone last season it will not be the same and it will not be easy at all to repeat their glorious 2022/2023 season.The other teams though so far have not done much in the player transfers during the summer so I don't expect them to have an easy win in the Champions,mainly I am referring to Real and Barcelona here.
It's difficult, but it's possible, if Real Madrid can do it, then other teams can do it too. City are probably one of the few teams that have shown very stable results in recent seasons and go far enough in the Champions League, so their chances are very good. What will happen to Bayern is not yet clear, the same applies to PSG, Real Madrid also did not resolve the issue with the striker, and this was evident in the match with Barcelona. So City will be the favorite in this Champions League too.