Can you elaborate on "fairly well documented exploit tactics"? My impression is that most of these are either social engineering, for which we need to hire better designers, or complicated chains of hard-to-find primitives only accessible to state actors.

There's definitely problems but the solution isn't to make the iPhone a general purpose computer. We definitely need to defend the existence of general purpose computing at a time where regulation is likely to begin encroaching on it, but the promise of the App Store is "pay a 30% tax and any app you download here will be safe." In my mind, at least, that's the promise, and perhaps one solution to the situation would be to erect consequences to breaking that promise.