Gundogan presence at least gives Xavi several options to rotate players in the main squad, it's true that Xavi hopes that Barcelona midfield will rely entirely on Gundogan, not a good option, especially at the Champions League level. However, if Gundogan is compared to the Midfielders currently owned by Barca, there will be a very big difference. Because Gundogan has more experience and experience than other Barca midfielders, in other words, Gundogan is expected to contribute to Barca's future appearance.
No player in the current Barca squad has ever tasted the Champions League trophy other than Robert Lewandowski and Ilkay Gundogan, Barca last winning it in 2015 when Xavi was still their captain. Gundogan arrival will strengthen the mentality of the other players in the Barca squad and will be very influential on the pitch and in the locker room. Next season I think they still deserve to be on the list of favorites even with a makeshift squad.
I know a lot of people are very interested to see how Barcelona is going to perform in the Champions League competition. I honestly do not think that we should have big expectations from Barcelona. Personally, I do not think Barcelona will go very far in the Champions League. In my personal opinion if Barcelona can actually reach the semi-final of the Champions League I will say that it is going to be a decent performance from Barcelona.
I also understand that you are trying to say Robert Levendoski and İlkay Gündoğan have lifted the Champions League trophy before. But they are quite old right now. So I cannot say that Barcelona is going to win the Champions League trophy because they are in the squad.