I have seen a lot of trailers reversed into expensive cars, flooded cars, trailers falling off and hitting things at speed, cars driving into the sea because the driver got out to check the trailer, etc.

A lot could be fixed with better software and sensors. For example a car should be able to measure the angle of the trailer and apply the brakes when someone tries to reverse-jackknife. It should measure oscillation frequencies and damping factors at highway speeds and set a safe max speed. It should refuse to start the engine at all if a trailer isn't correctly hooked up including electricals and brake lines, etc. Finally, trailer brakes need an overheat/wearout sensor so the driver is aware if their trailer brakes have failed before they find out when going down a hill at 70 mph.

As a kid we would sit down at our neighborhood landing in the summer and watch boat launches for entertainment. I saw at least 2 cars get submerged, people run into each other, many many fist fights. Prior to allowing me to pull our trailer, my dad made me back up (with trailer attached) in circles and figure 8s in a parking lot and then in and out of the driveway many times. Showing up to busy landing on summer holiday is NOT the time to learn how to back down a trailer.