Do you not consider the J-20 a formidable threat to your 5th generation platforms?
I do not. Am not saying the J-20 can be dismissed. But am saying that the phrase '5th generation' contains more than just the platform. Low radar observability has the same operational gap from '4th gen' as the jet engine has from piston. A seasoned pilot familiar with piston engines will be outclassed by a new pilot in a jet. The human factor is always important, but that is precisely the point. The pilot is able to recognize the technical advantages and exploit them, especially when the technological gap is immediately evident, such as transitioning from propeller to jet where the jet engine created an entirely new aviation regime, from airframe design to flight behaviors, the analogy here is parallel branches in an evolutionary tree of a particular species.
Likewise, low radar observability created a separate branch of combat operations from that of 4th gen platforms, and by that, it includes even the enemy. If you know that will be facing 'stealth', you must change your tactics.
Remember the OODA loop? Observation -- Orientation -- Decision -- Action.
To effectively answer your question, it is TTP. Tactics, Techniques, and Procedures. The US have nearly forty yrs of combat
Tactics for our 'stealth' platforms started with the F-117. No one else equals. So to answer your question, the J-20 is a technical threat, but not a tactical threat which is largely
HUMAN sourced. You can stop here or continue below.
Tactics is high level or in the context of military aviation, it is the squadron level. Obviously, a bomber squadron would have different tactics than a fighter squadron. The point about tactics is the question: What have the squadron done to maximize all the technical features of its aircraft. This is policy or management level, if you will. We can take this up to wing level as well, but policy at the lower squadron level is the most flexible.
Techniques is one more lower level at the four-ship unit. In combat, if you are alone, you are prey. It applies to the soldier as well as the airman. It could be a four-ship or a pair, but what techniques did the squadron create so that fighters in combat formations can maximize the aircraft's capabilities. The introduction of precision guided munition (PGM) affects techniques or how to deliver bombs. IR missile is best in a tail chase situation so what can a lead and wingman do in that situation.
Procedures is at the individual pilot level like the OODA loop. What does the pilot know of his aircraft and this is where technical education is stressed. If you put an F-16 pilot into a Sopwith Camel, he would not know what to do with the 'Mixture' knob. Conceptually, I know that 'Mixture' has to do with the fuel-air ratio and the knob controls that ratio. But I would not know when and how to use it effectively. I have no practical education of that technology, old as it is. Similarly, if you put a MIG-29 pilot into an F-16, from a jet with poor cockpit ergonomics into a jet where the pilot rarely have to take his hands off the stick and throttle, you will have a pilot who can fly but not as well as a pilot who is fully familiar with the uniqueness of the F-16.
Reverse it...
Procedures governs the cockpit actions or behaviors of the pilot so that he can effectively coordinate his aircraft with others to execute certain
Techniques that are unique to the aircraft so that the squadron or wing can create
Tactics that will increase the odds of winning a war, or at least the air portion of a war.
Put all of this together...
Can a B-17 maneuver like a P-51? Obviously not. But a fully loaded F-15E can carry the bomb load of a B-17 and still maneuver like a P-51. Then once the bombs are gone, the F-15E can outmaneuver the P-51. You have a platform that combined the best of previous generations and even surpass them under certain conditions. If you are the wing or squadron commander and if you cannot create combat tactics based on these unique capabilities, you should be court martialed.