De Gea is still quite good and even for now during his return to Serie A his performance is very good but of course it is also not a reasonable thing if Manchester United are looking for him again as an option for Onana at this time.
De Gea is already comfortable with his position at Fiorentina so in this case even if Manchester United want him back I think he will also think several times about agreeing to this.
Manchester United made mistakes in the past and re-signing De Gea is a step of redemption in my opinion. But I agree in another view because re-signing De Gea could not be so good because Manchester United have made a bad decision and inadvertently hurt his feelings. In terms of quality he is still pretty good and his average game at Fiorentina is quite impressive.
It is better to look for other options by bringing in a young goalkeeper who has quality so that in the long term they have a much better goalkeeper. Onana does need to be given a little pressure because with another goalkeeper there will be competition for a regular place at the club.