Both of Real Madrid's teams in the example are playing for the championship. It is necessary for Barcelona to make player additions this year. They have not yet transferred a player that will take them to the next level. Maybe Nico Williams could be one of them, but his transfer is still uncertain. Barcelona is a quality team, but they are very weak next to Real Madrid. In fact, they are a bit unlucky because Real Madrid has become very strong.
The way they played against Manchester City in the friendly match doesn't looks like a weak team. Flick might has its own style of playing and the same players can still be optimized for high yield performance and everything will still be fine. Who knows if Flick accept the job to used the already established players Xavi used last season, the club doesn't looks like they are going to get new boys.
However, I think no matter how they play this season, I don't know the magic Barcelona are going to use to play with Real Madrid. Their squad looks to over saturated to compete with, Anceloti is unbothered and they are officially closed for signing new players, that already has show their confidence for this season.