To stop signing players with so many handicaps. Antony, Casemiro, Ugarte, Onana, Martinez, AWB, Fernandez etc. One thing you note with all the big teams is that they hardly sign one dimensional players.
You can’t build a midfield when all your players cannot do all the basics of midfield to a mid table level.
Fernandez is terrible at ball retention
Cassemiro is terrible at all retention and passing and running with the ball.
Ugarte based on my limited knowledge seems to be the AWB of midfielders.
Barcelona have Pedri, FDG and Olmo . Guys seem to be good at everything you want your midfielders to be good at .
City Rodri, Gundogan, Kovacic. The odd one is KDB is more like Fernandez but not as bad with ball retention.
Arsenal , Liverpool, Bayern etc use the same formula.
Hell if you look at Anderson and Cleverly, Fletcher and Carrick, etc offered more in terms of midfield play than any combination we can field now. None of those players were world class.