A MANPAD can't hit a fast moving jet at 20k feet, and anything larger can be destroyed by conventional munitions. This is exactly what we saw during the first Gulf war, when Iraq - which had for the era had a very advanced IAADS - was torn to pieces by the teen fighters. A decent SEAD campaign + lasers = a new, scary kind of warfare.

This is, incidentally, why the A-10 is obsolete. Trying to fly slow and low on a modern battlefield is indeed doomed. During the Gulf War, F-16s performed more CAS missions than A-10s did because the A-10 was simply not survivable against modern threats. To the extent they had to be withdrawn from known Republican hot zones because the danger was simply too great.