You can have all the warning systems the design engineer/pilot wants. Eventually you'll have warnings to tell you that the warning is not working.
Bottom line is that you have to AVIATE. Sommebody has to mind the shop. Every manufacturer's manual I've read has stressed that at all times one pilot is responsible for Flight Path Control. It is clear that this didn't happen in this accident. That is the responsibility of the pilot-in-command - to ensure that one pilot is looking after flying the aircraft while the other one deals with the peripherals whatever they may be - radio, QRH, checklists etc.
In this case it is clear that none of the three pilots did that with disastrous results. The only question now is WHY.