I think we need to start distinguishing between different qualitative grades of "computer assistance" here. The executive decision of "fly north instead of east" is on a different tier than "increase angle of flap more than normal to compensate for under-performing in prior maneuver."
In the broadest sense, my car is not drive-able without computer assistance either, because if you burn out the computers the engine won't start.
But your average Cessna lawnmower engine is perfectly startable without computer assistance.