Xavi is an exceptional manager, he's already showing that in the league, worth remembering that this Barca team is a work in progress, which can be seen with their exploits in Europe. To be fair to him, he was also missing some key players, Dembele in the first leg and Pedri Gavi in the 2nd. It's not like we played them out of the park, both games were close, the DeGea miskick or the Kounde header, or the Lewa goal line clearance could easily have gone the other way.
People always complain about Pep not having a plan B and occasionally it does come to bite them, but it's not like there are other team with a plan B that are doing better than Pep's teams. Look at Arteta now, even if they don't win the league, you can't call him a fraud or just another manger, he's deserves credit for this season. This is Xavi's first full season with this team, there's so much going on in the background there too, and he's still, in all likelihood, winning the league.
Just because what ETH is doing is almost akin to magic, does not mean Xavi is not a good manager.