Russia attacks Israeli military aircraft, page-30

Maybe there is still the human error to be considered. Like when the exorcet sank the Sheffield off the Falklands. The Sheffield had the missile defence system, the Glasgow reported the incoming exorcets, fired chaff and took other measures. Officers on the Sheffield were too slow to react. Some officers were found to be negligent in the subsequent inquiry. You can buy good kit, but numptys in charge can still make it fail.