As for the mentality, this whole nonsense that Xavi used (joint meals, increased discipline, etc.) is a psychological pumping that gives a short-term effect. After some time, in my opinion, this rather gives a negative effect, now it’s not the 60s for players to endure this for a long time. As for the results of Barcelona, they have become better (but not in all tournaments hehe), but these are not the kind of radical improvements that allow them to hope for something.
At least in this case they have a little change considering that maybe in this case Xavi wants to do something from the smallest first such as providing a special approach between the coaching staff and players although I do agree with what you say because this will only affect the short term and not very good in the longer term but maybe this is something they really have to do now considering at the moment the players aren't too fit in their chemistry and hope all this can improve things for the better.