La is not for some random mediocre team. Xavi Hernandez was relived from his duties because the board simply want what's best and they've seen a competent coach which they probably solve the problem. Barcelona newly appointed coach, Hansi Flick is currently in charge we should expect the very best from him and Barcelona next season.
You seem to forget thst xavi Hernandez isn't a small coach and has got a good reputation even back then at Barcelona, he has been able to manage the team well enough even through their challenges, the best they have gotten since they had been through some challenges especially with finance, Barcelona have been able to scale through fairly even if they have not won a trophy in quite a long time, they have been able to still maintain a form in the la Liga, the good thing about xavi is in the fact that he was able to still get to use available players without having to really get the team spend on getting new players.
If Barcelona gets to do better u see flick, it still doesn't mean xavi wasn't good enough, I would even prefer not to judge flick by the results he will be getting in thw first season, buy been able to maintain rhat good results long enough I to two seasons will get me believing he was just a perfect replacement because Xavi was able to keep thw team in a relatively fair form and performance through two seasons even with thw challenges he had to face, so replicating everything in a better way will be the reason Flick can be considered as been better.