Barca really need to be more ruthless about players that are not good in general. It's been a problem at this club. It's simply the way it is when you are aiming to be the best. You don't have time to pamper players who aren't contributing.
You don't have to be mean or petty, but you do have to be firm. Think we can also rely on Flick on this as well.
The best move here was to sell him after it became clear he was having serious injury problems. It is hard to do that, and Barca often don't sell players until their stock is low (unlike Madrid), but this is where we need clear eyed business sense, since his youth days it was obvious he is disposed to very serious physical problems and therefore he couldn't have a future here.
Even as early as the start of last season I imagine we would have had decent fees coming in, or at the very least loans from worse leagues where he could show his qualities comfortably. Instead we sent him to Brighton in the Premier League which exposed that he is physically done. A loan to Portugal, Turkey, Holland etc would have been a much better bet.
I imagine that the top teams in Portugal and Turkey are likely closed off unless we pay the majority of his wages, because those teams have better and cheaper players. In Galatasaray they have players like Morata, Osimhen, Sallai, Icardi etc. Even Besiktas have Rafa Silva, Immobile, Semih. So, even teams like this who might have been interested in him before will know he is not at their level anymore.
Mid table or relegation teams in the top5 leagues will not have the finances to want to sign him, and the big European giants outside the top5 leagues have better options available.
It will be very tough to move him without him showing better performances, essentially, but possibly that boat has sailed.