Xavi is considered to have been able to make Barcelona improve more than the previous coach. Barcelona had a good game play and they seem to be getting into a rhythm again at the moment. The performances of Lewandowski, Dembele and Raphinha have made them have a strong attacker. But these statistics are also supported by good midfield, defense and attackers.
[1] https://www.whoscored.com/Regions/206/Tournaments/4/Seasons/9149/Stages/21073/TeamStatistics/Spain-LaLiga-2022-2023
I think what @ginsan is trying to say is that recently a lot of coaches have not been able to do well with Barcelona. Barcelona actually struggled a lot to find a suitable coach who will be able to bring in good results for themselves. But Barcelona was not able to find anyone worthy. Until Xavi came as the coach of Barcelona.
With him being the coach of Barcelona, we could see an instant improvement in the performance of Barcelona. It is hard to actually say that he is the only reason for Barcelona's success. But it is also not going to be very wrong to say that he had a lot of influence in the recent success of Barcelona in La Liga.
I honestly think that he took a very sensible and realistic approach to everything. He understood that this squad is not going to be able to win everything. So, he chose a target which is the La Liga title and he is concentrating on that. .