Mick that's an excellent technical point about that missile system, the lack of the kind of IFF integration that would allow for seeing more than just targets.
I strongly question your last sentence's validity. I am not convinced that these people are/were professional enough to have the kind of C2 and airspace volume control measure, nor charts and depictions, to either know or care if an airway or jet route was near where they were fighting. They are/were ground minded people, not air minded people.
The "fire blindly into a known civilian airway" is the way you or I, who have a pilot's point of view, would look at it. I strongly doubt that, these people being on the ground, not professional, and concerned about their local war, would even come close to looking at it that way.
Where you sit determines what you see, and may also determine what you are even looking for.
I completely agree, however, with your general charge of carelessness, in that they seem to have been of the mental mode of "I am looking for targets" with little other consideration given. From their side's point of view, that kind of attitude is what results in blue on blue. Sadly, a "neutral" is who paid the price.