Change is needed in every competition but I think Barcelona doesn't need to make changes for now because I think their squad is perfect enough to compete next season, Hansi Flick just needs to maintain what he did last season, but maybe the small shortcomings that need to be fixed are on the defense side because even though their defense is not bad sometimes the players like to make mistakes that result in defeat.
Btw I haven't heard the latest news regarding the purchase of Nico, has Barcelona not found common ground with Athletic Bilbao?
Having a perfect squad doesn't mean more players should not be added because having a perfect performance with less injuries does not guarantee the same thing in the coming seasons that's why more players are needed to have enough squad depth when injuries come in. The high line defending might be a challenge for them because other teams would have come up with strategy to overcome it. It's not easy to maintain same performance for two seasons with same players but let's see if Hansi Flick is good enough to make it happen.
They have financial issue and that has limited them on buying some key players that would have made great impact in that team, we all saw how Nico connected really well in the national team and that's why the connection was indeed needed because he would really help boost the performance of the team but due to financial restraint they can't meet up with his signing but hopefully they sign him.
If you see the caliber of players in Barcelona you will know that they facing financial problems that is stopping them from going for top players. We all know that they used to go for top players just like Real Madrid but now they can't afford to sign top players anymore. If they really need Nico Williams they will go and source the funds because Athletic Bilbao will not want to sell him below his worth.