I get that there's more things involved for a practical implementation (weight, reliability, added complexity) but still... What am I missing?
As mentioned there are alarms already, but you can drown it out if sufficiently overloaded. Its best to recognize overload, take a deep breath and go back when calm.
Pilots still land gear up, even with the alarm sounding. There is (or at least was) even a public (YouTube) video of this happening from a passenger filming.
Landing a plane is not difficult (source: I’m a pilot) but there’s a lot going on. This is clearly a UI/UX issue but innovation is relatively slow in the certified market.
And yeah, before anyone says "but the beeping!" - yup, people are fallible. I've managed to scratch a car in a similar but far cheaper setting: start up...set navigation...go into reverse...think about the traffic announcement...think about garage keys...hear parking sensors beeping...beeping intensifies...CRUNCH...facepalm, dammit I was supposed to brake! In my case, this was a low-speed, low-energy collision, so just a tiny scratch on plastic, but I can definitely see how a minor distraction can turn into a major accident.