Xavi may have left a solid legacy at Barcelona but even without all that, I think Hansi Flick will be able to achieve success with Barcelona as long as he has full support from the boss. Hansi Flick is a good coach, and I think Barcelona was very fortunate to be able to sign him to replace Xavi. The only problem that might be the biggest obstacle for Hansi Flick is Barcelona's financial condition which might prevent him from being free to recruit the players he wants.
Changing of the Barcelona's manager from Xavi to Hansi Flick may not be the only solution to Barcelona's problem currently. What's more worse than that is the case of their current financial constraints which they must faced and struggle on how to get out of the current financial issues the club is facing. This Financial crisis occurred as a result of the Covid-19 pandemic but more importantly as a result of the mismanagement of funds at the board level. Having just the name Barcelona is not enough to make the club stand in its legacy of being one of the toughest European clubs in the world rather it is how strong the management maintains the capacity of the club, financially and its workforce. Else, regardless of the manger that comes after Xavi and the present. They won't still be able to work effectively until there are finances.