Manchester United did the right thing allowing David De Gea leave but did wrong signing a goalkeeper like Andrea Onana. I get it though, this was a signature wanted by Erik ten Hag during his second season with the club so as to execute and project his tactics and style of play. Disregard speculations of David returning to Manchester United, he has been offered contract extension already by Fiorentina ( 1 Yr extension ).
But I think it was a wrong way to let De Gea leaving. In Fiorentina, De Gea shows that he has a better quality than Onana. If De Gea still plays with Man United, Man United may have no problem with goalkeeper position. To be honest, I don't really knows Onana but I think Onan is actually not really a bad goalkeeper. He only can't be as strong as we expect because Man United has fragile defenders. There is no way that Onana can perform optimally if Man United never improves the quality of their defenders.