That is more about how planes and cars are different than about how plane and Tesla autopilots are different.
When driving a car, if you take your hands off a car, you will crash within seconds. Either you will come to a corner, or the shape of the road will just cause you to drift off. You are always zooming past obstacles that are meters away from you. Often less.
Planes are different.
Even without an autopilot, the pilots have trim wheels that allow them to adjust all the surfaces so the plane flys excatly level and stable when they aren't touching the controls.
So even without an autopilot, the plane is able to fly for minutes at a time without the pilot touching the controls. Eventually the balance will change, fuel is burns and the wind conditions might change, but these things happen slowly.
All the autopilot really does is extend the amount of time the pilots can avoid touching the controls from minutes to hours.
The other major difference with planes is the available recovery time from any issue is much longer, at least when not landing/taking off. When planes are near the ground the pilots are require to pay just as much attention as Tesla drivers are, actually far more attention.
But when planes are at high altitude, pilots have tens of seconds to detect something is going wrong, disengage the autopilot and correct the attitude. There are no obstacles. ATC keeps other planes far away.
But with cars, you are always seconds away from hitting an object. The driver needs to be able to take over from the autopilot instantly.
Plane autopilots work great for planes. They simply don't transfer over to cars. The operating environment is completely different.