I disagree.
We have a world class goalkeeper, we pay a kings ransom to him. Over the last few years he's been exceptional, a league of his own. He's currently not at that same phenomenal level. We don't dump him - we challenge him.
Bring in Dean Henderson, tell him he's understudy to DDG, tell him to prove in training why he should be picked ahead of DDG and if/when DDG makes a mistake AND Henderson is training at the same level - chuck him in and then force Dave to fight for his place.
We can wing that for a season or two. Ultimately you can't keep 2 excellent keepers, so one will leave; as a club we need to ensure we keep the better goalie.
Also we could do some rotation, play 1 in the League and the other in the cups, like we do with Romero. Give them both game time to prove who's the better keeper.