At the start of the season, Barcelona played badly. some of the names you mentioned, are not playing as well as they are today, especially Gavi and several other players. there are many matches that barcelona won, despite the fact that they played badly. I, as a fan, don't really enjoy when they play the game.
In the second half of the season, not so bad though they play goes ups and downs. oh yes, since Busquets was paired with De Jong, Barcelona started playing pretty well. however, for wingers, the performance of the players fluctuated. well, for the defense, I don't doubt them.
You may need to look at Barcelona's journey in La Liga this season once more especially in their 19 matches in the first half of the season. If I am not mistaken, Barcelona has only 2 draws
"Rayo Vallecano and Espanyol" and 1 loss by
"Real Madrid" in 19 first half matches. Then how do you say Barcelona's form was bad in the first half of the season?
Check here:
https://www.livescore.com/en/football/team/barcelona/2911/results/De Jong, Dembele, Lewandowski, Pedri and Gavi and Raphinha played well. They seem to hit it off with Xavi who is so passionate about his team. But unfortunately, Barcelona failed in the Champions League because the opponent was quite heavy. Barcelona also failed in the Europa League because of Manchester United, but next season I hope Xavi can make his dream come true.