I think Barcelona's midfield is not their main problem. The main problem is that they were facing a club who put the whole of its players behind the ball. They struggled to enter their opponent's penalty box. But, they were lucky. Their opponents were unprepared for their attack for a moment. And they scored the only goal from their striker, Lewandowski, to get three points. And their coach, Flick, paid attention to all positions. He knows their midfielder did not urgently need a small change.
I think their opponent understood that they are a tough team and must have seen their records since this season so they got prepared so they don't get to be humillated probably (lol) with a high winning margin. they successfully made their defense almost not penetrable by their opponent such that the only chance their opponent got was that which they used to get a goal that kept them ahead. Barcelona would have almost ended the game in a draw but luckily for them they were able to get the complete three point at the end of the day. Lewandowsky is still very much of a key player for Barcelona and flick knows about that so well and that's why he's not ready to change him at the point when people taught he should have.
The formation used by Getafe was really effective enough to stop Barcelona's attacks which were continuously bombarding Getafe's defense. There were even one or two moments where Getafe was able to make a pretty good counter-attack and almost made Barcelona's defense falter. Getafe could even score a goal in that match if they really had a better striker. Getafe lost the match. But they earned my respect for their defensive toughness.
Barcelona has once again proven that they are still unstoppable at this point. And I think that in the next 3 weeks Barcelona will continue to win matches in Laliga. And maybe the tough test for Barcelona will begin when they face Real Madrid in week 11.