They are theoretically a safety layer when we have proven they work. If they do not work well, then they aren't actually safer.
The AVs do not work well in the edge cases - exactly in those situations where humans can apply common sense and behave accordingly. Exactly the cases that sceptics seemed to be worried about, and it turns out that the sceptics were right.
I hope AVs will not be allowed on public roads where I live in the next decades.