Having worked on a test range where even the best Test Pilots had trouble finding dayglo targets at pre-briefed positions, without being shot at, I feel sorry too for the pilot/s involved unless something proves otherwise.
At low level & high speed in a fast jet ( don't know the circumstances of this tragedy ) no-one has time - seems to me from my comfy chair that laser designation - which I worked with - is the only thing to use; not experienced with GPS weapons.
Do our guys have enough designators ???
P.S, I am well aware that such things as a bomb retarding fin deploying late or not at all, or some such sod's law, will make the best kit fail...