And the average human driver is terrible at driving
There's tons of people on the road, so there's plenty of quite bad drivers you'll encounter every day.
But driving is relatively easy. Saying that the average driver is terrible seems like a bit of a stretch.
I'll give you that there's millions of terrible drivers. That doesn't make the average terrible, though.
The fact that we're all not constantly getting smashed into means that on the whole drivers are competent.
On a typical Texas highway not only is everyone driving 10 over, and the typical following distance is about ~1 car length. At 80 miles an hour. Lord have mercy if anything happens on the road.