Honestly, I really regret Barcelona's defeat in the second leg of El Clasico Copa Del Rey yesterday. I didn't see what they lacked in the first half, but somehow it ended badly for Barcelona in the second half. Apart from the midfielders, I think they also lack defensiveness and are not effective up front. Lewandowski didn't have many chances, while Raphinha did too, which kept them from scoring until the end.
But I appreciate Barcelona's struggle even though I'm disappointed. This El Clasico is good for Real Madrid, but we have won a lot of El Clasico this season. I'm not saying it's fair, but it's clear that Xavi has problems between his players.
The second half of Barcelona's game was a complete mess, all Barcelona players were not well coordinated with each other, especially the midfielders were unable to create opportunities to send mature passes forward and made it difficult for Lewandowski to score goals. I agree with your analysis, that Barcelona's weaknesses are on almost all fronts in the match, but what stands out the most is the midfield in my opinion.
Two or three El Clasiko wins earlier this season broken up by a semi-final loss, can I put it that way?
I will also tell you the same thing, that Xavi had problems against Ancelotti in that game and his tactics were easy to read after the First half and there was no solution when he conceded two goals, so Barcelona's game was even more chaotic.