Because there is no way for them other than trying to continue with their youth especially for young players to be able to play stable when Barcelona needs to rotate players and focus on several competitions at once.
Flick is currently trying harder to prove that he deserves to replace Xavi as coach and of course the initial achievements are important where they are definitely pursuing the target of several trophies at once as a plan for this season, especially for the focus is the Champions League which is indeed in the Xavi era sometimes not too good for them.
Flick knows that young players are future of Barcelona and in their current squad, they don't have enough good experience players to play and rotate in a long season, so he decides to use young players more aggressively. Only few weeks ago, he got a lot of applause for his success with Barcelona and young players by this strategy. After some bad matches recently, he got massive critics, that is unfair for him. Barcelona must accept a fact that they are rebuilding their team, and has to forget an ambitious thinking like they can win La Liga in this season. If they can win it, it's perfect season ending for them but if they can not, it's not terrible ending for them.
Fortunately in this case the rotation and progress of the development of young players is going well and indeed Barcelona continues to maintain its characteristics that are slowly reappearing after several eras by not trying to maximize Lamasia who is actually very productive. This is indeed a risky move but in the end this also pays off with the results that have in the end so that Barcelona still remains in a comfortable condition in terms of players even though in financial terms they are not safe.
Now the focus is certainly to improve the performance that in a few weeks was lost and a big win this week will certainly make their condition more confident to continue playing well.
It's been a different story for our rivals this week, as I had high hopes for Madrid but they dropped points again with a defeat.