Using Autopilot in a Tesla makes you less safe. Search the forum for "phantom braking" -- that is my main concern (technically that is not part of Autopilot, it's part of Traffic-Aware Cruise Control which in my mind is a subset of Autopilot). The system will slam on the brakes when it thinks there's an obstacle in front of you, and it is really bad at deciding what is an obstacle. Shadows on the road, cars in the lane next to you that are driving perfectly fine, berms on the side of a curved road -- these are things that have caused my car (2021 Model S) to slam on the brakes, including while driving on the interstate at 75 mph (shadow of an overpass). When I have TACC turned on, I have to cover the accelerator with my foot, so that if it brakes unexpectedly I can hit the gas to stop it in the act. That is the opposite of what you should be doing, you should be covering the brake in case you need to stop. It's really embarrassingly bad.
The problem is particularly bad with Teslas -- most cars do a much better job from what I understand. Maybe if Tesla used LIDAR instead of cameras...
Autopilot does encourage a lack of attention. Driving around town I have gone straight over potholes that I would have simply steered around. I don't think it would do well if a deer jumped in front of you. I trust my reaction time better than the system's (I have had near-misses w/o AP where I manually swerved to avoid animals). More evidence that its reaction time is poor: several times a car has turned in front of me, but plenty far ahead that it wasn't a problem. After the car has already cleared my lane, the car slams on the brakes!
As for Full Self Driving, I would never trust it based on what I have have seen and read. I realize it's a "beta" or whatever, but if you don't watch it like a hawk it will drive you into a curb or a parked car or something. Plenty of YouTube videos showing things like that. (I do not, and will not have that on my car).
So, if I had a teenage driver in my family I would instruct her to never rely on stuff like that, and to assume that using it is more dangerous than not using it.