Car safety is not single way, it is also what the car does to others, which has not changed. Also humans have not changed, we still have same limitations, which might have got actually worse because people rely on those "safety" gizmos. They think they can drive faster, when they can't. Laws of physics are hard to dismiss, car is still heavy mass moving at high speed, they don't really stop much faster no matter what you do to suspension, tires or brakes. Just slight fender bender with a cyclist is bad for that cyclist. Car that is hardly even moving can kill a pedestrian.

The fact that car can go faster doesn't mean it should go faster.

There are places where speed-limits are set too low, I agree, but that doesn't mean that they are set too low everywhere. Sometimes the reason why some place has lower speed limit is not always obvious, maybe there is a crossroads blind spot behind next hillock, maybe there are small children getting in or out of school at this straight as an arrow road section, things like that.