The challenge self driving cars face is that being "overall better" is probably not enough. Regressions in certain segments would hardly be acceptable for anyone. You can't tell people "FSD cars lowered overall deaths by 10% but we now kill 30% more toddlers because [technical reason]", or that "highway deaths are going up", or basically any segment that anyone could reasonably care about. Cars have to match and exceed human drivers in every category for them to be acceptable, and even 99% there may not be enough.