We are aware of it, but it seems like Barcelona is not aware of that at all. They keep trying to put some managerial changes when in fact the problem is with the financial situation.
Koeman, Xavi, Flick none of them could do anything about this team because they lack the finances to make this team better, Xavi winning the title was a huge shock and they should have kept him for that reason, but even with Xavi, or any other manager in the world, they are not going to get better. Hell, Real Madrid just got Mbappe for free, can you imagine how great you have to be in order get him for free? Who did Barcelona get for free? Ilkay? I am sorry but Barcelona doesn't have a manager problem, it has a money problem and that's not going away anytime soon.
I agree with you that Barcelona management should have allowed Xavi to remain as their head coach since he managed to win the La Liga title in his second year at Barcelona. Barcelona is a good club that is known for winning trophies, but since their financial situation changed, Barcelona has found it difficult to play competitively and win trophies. A coach can perform well at Barcelona only when they fix their financial problems so that the coach can be able to buy the players he needs in his squad. Flick will not turn things around at Barcelona because Barcelona needs money to overhaul their squad.
Barcelona's management has been very problematic lately and has been too hasty in making decisions. Many were disappointed with Xavi's dismissal, because at least Barcelona did not perform badly throughout the season, even in the previous season they managed to present the Laliga Trophy to Barcelona because the defense that Xavi had built recently showed very good development. It's just that they have a lot of injured players like Gavi which means they can't compete well in Laliga this season. Apart from that, Real Madrid is in good condition so it is natural that Real Madrid won the Laliga Trophy.
In the hands of new coach Flick, hopefully the chemistry of the Barcelona players will remain intact and we hope that Xavi's dismissal is not a blunder on the part of the management. Flick is of course very happy because Barcelona's defense has not changed much, he only focuses on the midfield and attackers to be able to play effectively in scoring goals. Flick is known to be good at polishing young players, so that even if he doesn't buy new players, he can take advantage of existing players. Maybe that's why Barcelona management recruited him, but I doubt that next season he can compete with Real Madrid in the race for the La Liga trophy.