I completely agree with you, but the counter argument is the only incidents that are getting through are the ones that are solo because the more complicated plots are getting intercepted and disrupted.
The problem with this argument is that it can't justify continued spending because that would make it unfalsifiable. We need to spend $450B/year on a bear-repelling rocks because we currently pay for the rocks and there are no bears. And if any bears do appear then we obviously didn't have enough bear-repelling rocks and we need to start spending $900B/year.
If there is a real question as to whether the ~0 bears is a result of the rocks, it's time to cut the bear-repelling rock budget in half and see how many bears there are next year. If it's still ~0 then it didn't need to be as high as it was and it may still be too high.