You can compare these levels of progress, sure but that doesn't mean the comparison is valid. Lots of people dismissed flying cars in the 60s and heck, they were right, the problem is fundamentally different.

The difference because the horse-to-auto transition and the auto-to-self-driving-auto is that autonomous cars solutions are inherently fragile and cars reasonably robust. (Flying cars are inherently fragile too - the problem isn't get a car-like-thing to fly, it's getting it to not hit things).