I pulled this graphic from another thread, but he really lacks variety in his passing range. Makes it too easy to press, his goal kicks either go short around the box or are humped long. Almost nothing in between the box and midfield, we can blame the midfielders, but let's be honest if he was capable of breaking the lines and putting the ball in there with the speed and accuracy required he'd be doing it more often.
https://theanalyst.com/eu/2023/04/david-de-gea-man-utd-replacements-costa-raya/
Compared to Costa.
It just makes it way too easy to press.
You press high he goes short to the defender, there's a lack of options, it goes back to him, it goes long, and it's easy to pen them in. Because he can't play that breaking pass into midfield.
If you force him to go long, invariably the other team wins it, because the forwards don't really like challenging for the ball in the air. And he llikes playing those high floaty balls out that make it even easier for defenders to judge and win.
Having a keeper who is a better passer and can pick out those mid range passes into midfield, creates a versatility in terms of building out, teams then have to think about pressing high, because you can pick them off in between the lines. A better long ball player and you can pick them off with longer more direct passes.
The result is you are more likely to create superiority in the build up phase, which then creates space further up the pitch for the other players in midfield and forward areas to operate and maybe string more than 3 passes together.