He is just another mediocre manager but no one can coach this team anymore. Since Messi walking mode has to be tolerated we would basically need to have 10 unbelievably fit and hungry players surrounding him but instead we now have 8 out of 10 of players that are well past their prime or are lazy as fuck so of course this doesn't work and never will.
To be fair, from this team in ideal scenario I would just keep Messi, Griezmann, Mats, De Jong and Fati (because he is very young and talented) but the reality is different and will suffer for some time until our board changes and our seniors retire.
Lets be realistic, just look at others:
Our attack: Suarez is grandpa, Dembele is injured 24/7 and has a low IQ.
Midfield: Busi was done 2 years ago, Vidal is also past his prime, Rakitic is done, Arthur is probably the most overrated player we have, Puig is a 15y old girl
Defense: Alba my biggest disappointment. I always thought he is a world class but this guy is a crybaby who never shows up in decisive games. All other fullbacks are just trash (Semedo, Wague, Firpo, Roberto). Our CB's are also horrible, Pique is done, Umtiti will probably never regain his form, Lenglet should be our 3rd option in ideal situation.
Unfortunately that's our current state and no manager in the world can change this in a few months without a full support of the board.