Barcelona has been performing well against big teams this season. We have seen Barcelona win by big margins in both matches against Madrid. Barcelona has also won by big margins against teams like Bayern Munich. But Barcelona has failed to win against teams like Getafe, Leganes and Las Palmas in La Liga.
I will say Barcelona performance is just fluctuating because for them to win two El Classico in a season with a very wide margin in goals and they are still finding it difficult to beat the bottom teams, that means something terrible his happening which is far from us. I don't think Barcelona are in their best interest this season because if you tell someone that Barcelona defeated Real Madrid and Bayern Munich, and lost to Leganes at Camp Nou. This is abnormal for team like Barcelona.
It is still possible for Barcelona to occupy the top spot in La Liga. However, for this, Barcelona will have to perform well consistently. I think Hansi Flick is probably more interested in winning the Champions League title this season. That is why Barcelona is not giving full effort in La Liga matches. Hansi Flick should be more aware in La Liga matches.
Barcelona is a team that is capable of topping any competition they play in a season because they have what it takes to do so. I don't know what Hansi Flick planned but if correct with your statement I will say he is bringing himself down. At the beginning he started well, then what bring a sudden change of plans, at least he should have planned it well. I think you just want to cover for his actions.