> Surely the copilot can look at a map (when I say map I don't mean a piece of paper -- I mean a digital one with GPS and everything) and see their trajectory while the pilot is landing, right?
It's not like the pilot doesn't know there is a parallel taxiway. Of course there is. They would be (subconsciously anyway) looking for it to complete their mental map. It just went wrong in this case.
You wouldn't even have needed a fancy automated system to realise you were looking at a taxiway in that particular situation. There were four big aircraft on there, with position lights and taxi lights and everything. And apparently visibility was good. It was just a spectacular brain fart.
While the system you're suggesting might give better situational awareness, it might also be a dangerous distraction in other cases -- or be wrong for some reason. So more tools aren't automatically better.
In this case the existing system actually worked flawlessly: another controlling instance (the tower controller) discovered the error, took appropriate action, and all that happened was a 15 minute landing delay and a good story. Probably happens more often than we'd care to imagine.
> Like I'm imagining there should be something on the plane that shows them their trajectory and the runway information. If there is, why isn't it telling them when they're going the wrong way?
Well, there's the ILS (instrument landing system), but pilots like to land manually. IIRC it's recommended these days, just to remain in training. I suppose it's also fun.
Also, ILS might be wrong somehow (interference, technical defects, the pilot accidentally entering the data for the left runway when he was told to land on the right, etc).
So the truth is this was just human error, and that kind of thing just happens. You know the saying: if you make a system idiot-proof, nature invents better idiots.