If grandma ignores my advice and installs the unsafe app despite the steadily more large and screaming warnings doesn’t that become individual responsibility at some point?
But what do you want to ensure: that grandma only installs malware on her phone via mistakes she is individually responsible for, or that she doesn't install malware on her phone? Maybe for the abstract 'grandma' you would take the first option. But for someone you personally care about, you're not going to choose the option that predictably ends with her being harmed, even if it will be her own fault when it happens.
You may notice we don’t cover all power outlets because kids (or grandma) may stick their fingers in them either.
I trust them not to do that.
Then again, if iOS has a setting that ‘enables’ the unsafe app store I’m confident grandma won’t reach it since it’s hidden behind the actual passcode, not a fingerprint.
And when grandma gives all of her retirement money to scammers by hitting the wrong button, she will get her rightful comeuppance dying on the street instead of taking up your guest bedroom.
In the real world, avoiding mistakes is more important than people suffering the consequences of mistakes.
You’re free to argue that, but my guess is that Apple actually cares about customer satisfaction regardless of who you or anyone else decides to blame for any particular instance of dissatisfaction.
