Thing is barca has a lot passengers in his squad. Coaching change is not going to improve anything much unless the holes are filled up.

Let's check out Barca's squad :

ter Stegen: once he was compared to Oblak, now he drops stinkers every other game.

Pique, Busquets, Roberto, Alba: they have been liabilities in defense for years. When they are starting, you can't compete against physical teams like Bayern, Liverpool or Atleti. It has been shown again and again.

Aguero, Dembele: Always injured. Not reliable players.

Neto, Braithwaite, Luuk de Jong, Coutinho, Umtiti, Lenglet: Passengers.

Garcia, Nico, Demir, Puig: youth, potential but still raw.

Dest, Araujo, Mingueza: they are very good players who are probably going to be undisputed starters by end of the season.

Gavi, Pedri: the two guys with great potential but they are still 17-18.

Fati: still coming back from a long-term injury. He is still 18.

FdJ: the only truly undisputed world class player.

Depay: the new signing, probably the only other world class player thsn FdJ.

There are basically only 8-9 good players u-22 players and two world class players. No fit strikers or wingers. You can't really expect win anything based on current squad. Neither Tuchel or Guardiola can do shit without getting at least 4-5 good players in positions such as striker, winger, center back, left back and CDM.

Disclaimer: I'm probably a lot harsher here. I will also say that my assertion isn't completely correct but but it is a lot closer to the reality than we are willing to admit.