Xavi was able to finish the season well in La Liga, but he failed to do so in the Champions League. Perhaps he has little experience in such competitions so far and it is easier for him to focus on one thing at a time. I think that in the current Champions League season Barcelona will not achieve great results again, because the competition is very big.
Xavi played in the Champions League last season and was later demoted to the Europa League and still got evicted in the end. He has experience both league while also focusing on his main goal last season which is the La Liga title which he won. After his qualification to the Champions League competition this season, he must have been preparing well to excel in both leagues. I’m expecting to see a big change in their game of play in both competition and won’t lose focus in any of them. Manchester City did it and won a treble last season, with a good coach this is achievable for Barcelona.
You can never say Xavi's experience in the previous Champions League as a player could ever help this player to have a better performance as a coach while coaching Barcelona.
If I'm not wrong, he never coached any teams in the Champions Leagues before and Xavi is a completely inexperienced coach in this tournament. Since he had no experience as a coach but got good results in La Lga with Barcelona we can expect to see the same thing from him in the Champions League.
I have a slightly different opinion from you. even though Xavi has only won titles in the champions league in the past when he was still a player but that does not mean he can not be a coach who can lead his team to win the UCL title. I mean Xavi has had experience at UCL as a player and of course he knows how the team plays at UCL so that the opportunity to become a coach who is successful in bringing his team to win the Champions League title can happen and break a new record when he succeeds as a coach for a team that can lift the champions league cup.
but unfortunately all of this is in the Barcelona players who currently do not have reliable players or players who have reliable talent to be able to compete with other teams in UCL.