Every other serious club has spent big (when needed) to ensure the GK is suitable. The first thing Pep did when he went to City was bin off Joe Hart (who himself was Englands #1 at the time). Klopp spent big on Alisson, Arteta replaced Leno with Ramsdale etc.
Quite simply we cannot play modern, progressive, high line football with De Gea in goal. Every single CB we have signed since Rio and Vidic have looked crap - the consistent factor is the keeper behind them. He doesnt communicate and he doesnt sweep to collect the ball. For a slow CB like Maguire its a nightmare match, because he (and the other CB) simply have so much more ground to cover than their equivalents at other clubs.
I wouldve had Henderson as #1 last season and certainly this one, or if not him then go out and buy a new keeper. De Gea holds us back, possibly more than any other single position (except maybe DM).