The problem is, we don't have anything to throw against their older fighters either, eg. the F-18 Hornet and the F-16 Falcon. These planes have been around and their bugs have been worked out. Secondly, pilot quality really matters a lot. A good pilot can take an old plane like a Mig-21 or a Phantom and still put up a good fight. Thirdly pilots matter more than planes. Running out of good pilots kills an air force. Planes can be replaced in a few weeks, pilots take months/years of flying experience to mature. This happened to Japan, in the end they even recruited the pilot teachers. When the teachers were killed it was over. So there need to be plenty of good pilots in reserve, and keep the teachers alive!