Earlier quoted context omitted.
Most Boeing planes (though not the 787 discussed here) don't use fly-by-wire, so you could argue that the most essential control plane is perfectly isolated by virtue of not having any sort of network at all, just hydraulics into the cabin.
But wasn't the 737-max issue that a software system was forcing an elevator change to pitch the nose down? That sounds pretty fly-by-wire (even if hydraulics are involved).
Instead we got MCAS which was messing with autotrim signals and escaped scrutiny.