It's not about comparing the two keepers , you can only pick one at a time and it's widely considered a very different job mentally than any other position, regards pressure , focus and resilience.
To drop a keeper as soon as a mistake is made is a ludicrous proposition to work under as a keeper surely ,and won't do anything to settle the one position that needs it.
Outfield players can share roles , be subbed put in a cameo performance and loads of other shizz, Pope face shoehorned in his new man at the expense of having a settled defence and it's no coincidence the amount of leakage there has been since