I think this El Clasico is not ideal considering that many players in Xavi squad are injured, and those who have just recovered are not yet fully 100% fit. On the other hand, Xavi took quite a big risk when determining the starting XI yesterday, which turned out to be true because he had to admit the greatness of the strategy implemented by Ancelotti. Dembele and Ansu Fati were released because Xavi wanted several players like Felix and Cancelo and to make room for young players like Yamal.
Regardless from this defeat, Barcelona also still has a chance to retain the La Liga trophy, the difference in points is not too big and it is still reasonable to catch up in the following weeks. On the other hand, Madrid is in top form at the moment, so it's not easy to beat them, especially with a player like Bellingham.
This is not the time for excuses; Real Madrid played excellently and deserved to win. Barcelona also put in a lot of effort in this game, but luck was not on their side, and they were unable to convert all of the chances they produced into goals; it was a sad day for them, as well as a day to make changes to most of their playing patterns. Regardless, as you've stated, Barcelona is still in a strong position to win La Liga despite losing the El Classico to Real Madrid. I'm confident that Barcelona will win the second leg of El Classico at Santiago Stadium, as it has always been a tradition in the El Classico. Ancelotti made use of a good strategy and at the same time Xavi, but Ancelotti succeeded over him in the end.