Black box data is retrieved analyzed and scenarios are prepared for pilots to train against.
I used to work in flight simulation and have flown a few different types. I designed the UI for the malfunctions/preselect system and while we had the head pilot trainer in to test the system one day we decided to mess with him.
We gave him a 35kt cross wind. Failed 2 out of 3 of the engines, as well as various hydraulics systems. Aside from the hilarity of watching the simulator engineer following orders to hand-crank the imaginary landing gear, the pilot made a near perfect landing without breaking a sweat.
I've had enough times in sim cockpits to confidently say that I could land a commercial aircraft if necessary. I can also confidently say that it would take me a dozen attempts to make that landing without crashing. Let alone a clean almost textbook touch down.
A landing attempt by a passenger as shown in the YouTube video would probably end with a crash since some manual flying is involved in the end. It is very unlikely that a passenger would getting the controls right at the first time and he (or she) would certainly not be able to perform a go-around.
Autoland would be more helpful. In the worst cased, an aircraft can land without flaps and without 'three greens' if the runway is long enough with a high probability of survival for the passengers. Speed control is of course important but the correct speeds for a zero-flap landing could be given from the ground via radio.
Hat-tip: Cabin Pressure, BBC R4
Pilots know flying is very easy, all the training is learning how to survive uncountable emergencies and failures. And economics and judgment and experience and doing it smoothly and a few other things.
Landing a large jet is very easy in a simulator. A random untrained person saving a plane that's out of fuel is impossible.