That's not an assumption but a reliance for IFR. You clear your path with air traffic control before engaging the autopilot. Collision-avoidance is not part of the autopilot in aircraft. And the pilot decides on the path.

In conclusion there are few similarities between an aircraft pilot and driving assistance in cars.

It was not an autopilot that crashed the two jets! Even if it had been, that would not change the fact that autopilots are a solved problem for IFR. The operating conditions where they can be used are clear, regulations are in place, and the risks are known.

I'd actually compare the Boeing "assistance" to the Tesla "assistance" as sometimes the craft will decide to steer into solid objects based on misinterpreted sensors. But the comparison is a stretch.