The issue is that the F-35 when it's actually being competitive is practically invisible. The US actually has generally had to operate it without stealth coatings or while broadcasting a radio beacon while doing comparisons or competitions against other crafts and weapon systems because in an actual combat environment, an F-35 fit for stealth is completely invisible to electronics (and to a measurable degree eyesight) well within F-35 weapon systems' effective ranges.

So essentially you can't see an F-35 until it is already lined up to kill you. That tends to make it pretty difficult to hit it.