Fortunately Tesla has/had some very smart people working on it. IIRC they figured they needed about 5-6 Billion miles driven/recorded for it to be "2-10x" safer than a person, according to youtube videos by Sterling Anderson, which is a great way to learn about how Tesla is doing autonomous. Anyone remember if those miles recorded included cars with the early sensors or is it just from the cars with the newer sensor systems?Full autonomous driving is super difficult. This is by far the hardest technical issue Elon ever faced, much harder than landing the rocket. I think eventually Tesla will solve it, meanwhile the autopilot will improve dramatically because of their work on L5.
All the other guys (Waymo, Uber, Volvo, GM, Nvidia ...) who claim they are close to achieving full autonomous driving, probably only got 2% of the work done. The few difficult cases is 99% of the work, and it can't be solved by piling person hours.