biggest issue here isn't memory safety but the dumpster fire of imessage format that calls out to privileged parts of the system
Will it make attacks impossible? Probably not totally. But it might raise the cost of the attack by an order of magnitude or more and certain classes of vulnerabilities might disappear completely.
"Jeff Bezos was hacked by a file sent from the WhatsApp account of the crown prince of Saudi Arabia, Mohammed bin Salman"