You’ll be able to change default apps soon in iOS 14 iirc. (Like replacing safari with Firefox or chrome) it’s a much needed feature to iOS and I can’t wait.
while I like safari and all default apps in iOS, it’s nice to have a choice on what to use. Like if I wanted to replace the default mail app with another, better app.
I believe that Apple are "considering" allowing users to change their default apps, so it's not set in stone. But even then, I refuse to believe that Apple would give full total control to a third party app. Just goes against everything they've set out to do until this point.