The biggest problem is communication. The best thing you can have, more than some idea how an aeroplane works even, is knowing how to talk to the ground. If you're talking to the ground, you get both practical benefits (people on the ground know how to fly that plane, and know what you need to do to get it back down safely) and a morale boost.

Chances are if you're taking over in an emergency, the radios are already tuned to a frequency with other humans on it, and you just need to know how to talk (there's a push-to-talk arrangement) and how to listen to what they say back. If you need to tune the radio that's already bad news, but if you happen to be reading this thread you want 121.5 MHz aka "Guard" and once people realise you're serious you should get help quickly.

The big plane can in principle perform the entire landing and roll out at a suitable runway, it's called a CAT IIIc landing. No hand flying is required, much less knowing the full "from dark & quiet" procedures. But arranging for that to happen is going to need communication with the ground. Most scheduled flights don't actually perform an automated landing of any sort since that would leave pilots rusty, and so your intended destination probably isn't capable or isn't set up to do it - but if a non-pilot is now flying a big plane that's not "most scheduled flights" that's an emergency, and so the fact that the only CAT III runway is currently being used for take-offs, or is closed to repair the markings, or is at a different airport on the far side of the city, does not matter. They will do what it takes to get you down safely.

The reason we don't use CAT IIIc landings ordinarily is that unless there was an emergency they don't solve a problem we really have. The CAT IIIc landing puts the aeroplane safely on the ground (good) but leaves it on the runway, where it's a hazard to everybody else. Under IIIc conditions a human can't see a hand waved in front of their face - which is why the landing was automated - so taxiing is impossible. If you're a non-pilot who just saved 200 people's lives that's not a problem, you're down safe now. If you're a commercial pilot with six more commuter jets stuck behind you on a Monday morning it's terrible so we just close the airport to all traffic in those conditions.