I understand your point, but I think that this is something that has, to my knowledge, never happened to a US commercial carrier before. This would indicate that rather than spending vast sums on technology - ground radars asked for in one post, RFID schemes in another - it might be more effective to simply remind pilots that they should take off on runways designated for commercial traffic. Of course the crew of 5191 has already accomplished that for everyone. No need to do much else, I'd argue, except keep the focus where it belongs, crew performance.
Who knows what was going on during the taxi, but there is just no reasonable excuse for doing this. As an example, there was a small cluster of incidents in the 90's where pilots were landing at the wrong airport. There were at least 2 incidents with commercial carriers. The publicity was bad enough, and I doubt the pilots involved escaped with their careers intact. Since then I've not heard of anything like that happening again. Certainly this incident will have similar corrective effect.
That's certainly a good point...
The main object is not to assess blame but to prevent crashes. Saying that a crash occurred because of negligence does nothing to prevent crashes. The system must be made as "stupid-proof" as possible. Lowering failure rates almost always happens because the process is improved, not because people perform the same old processes better. Telling everyone to be "extra craeful" does nothing. Behavior will almost always drift back to its previous state.
I'm sure that negligent and foolish mistakes happen all the time in our aviation system. However, crashes are rare, and getting rarer. This is because of the multiple redundancies built into the system, often from lessons learned from crashes.