I don't think the coach will have a big impact as long as the players stay the same. The condition of the players is very important for Barcelona. If they transfer players who cannot adapt to La Liga, they cannot bring success to the team. Robert Lewandowski still could not show his performance in Bayern Munich. They definitely have to reinforce the midfield. Likewise, they have problems in the defensive zone. The coach should follow these. I don't think it will make a big difference if it starts a new year with the same players.
In football this is not the case, the coach will have quite a big influence on the difference, so even though the players in the Barcelona squad remain the same, the team's performance will certainly be different next season with a new coach, but for better or worse we still don't know.
If we talk about Robert Lewandowski, he is no longer young and there is not much support for him from other players, so it is quite difficult for Robert Lewandowski to make a big contribution to the team.
Hansi Flick's task is of course very difficult, with all the problems currently existing in Barcelona, it requires him to build a Barcelona team with all limitations, but Hansi Flick can still go through this process slowly.
I believe that Barcelona management also wants them to get up quickly, everything just takes time and we just need to wait for them to get up and return to competing fiercely with Real Madrid for the title so that La Liga becomes competitive again.