You are confusing current drones with completely autonomous drones - which don't yet exist.
Yes, you have to train the drone pilots. Just because they can play an FPS in their sleep doesn't get them away from practicing.
One day we MIGHT have autonomous air superiority drones - right now we don't have them. Ergo, we can't replace the manned air superiority fighters just yet.
Can we do that eventually and cheaper than the F-35? More than likely. Can we create air superiority fighters that are 90% as effective as the F-35 and 30% of the price tomorrow? Sure we can.