Instead of writing this big long post you should've compare the design of both Rafale and J20 and you would've understand the things better. Emotions won't get you nowhere especially in a combat zone. Your pilot training, tactics and experience won't compensate the shortcomings of your hardware. If we talk about Rafale against the J16, J10 (And even the 'J20' only if Rafale and J20 dogfight) than we can talk about the pilot training, experience and tactics but the moment the enemy upgrade themselves a level more (4the gen to 5th gen) that moment we better upgrade ourselves too cuz in the BVR fight the probability of the 4th gen non stealth fighter getting shot down by the 5th gen is much higher. And about the privilege of having the notion of 'chinese made products' is inferior compared to the what you have can suit you europeans who neither border china nor have to fight a bloody war and if someday your notion of their real capabilities turn out to be false than still it won't cost you a dime but for us it's different, we cannot undermine them and if we do the results will not preety for us.
Your talk about 'retex', 'evolution', 'virtualisation', 'modularity as main phylosophy design' won't stop the enemy radar from reflects of the Rafale's non stealth body, it's outboard mounted pylon and weapon, it's fuel tank and light the enemy's radar screen as a christmas tree. You can upgrade the Rafale's radar, ew, avionics and softwares as much as you want but still it won't be a stealthy 5th gen platform. Ask Finland and Switzerland why the choose a stealthy platform if Rafale can do all the things that a 5th gen can.
And about the question of how AMCA can solve the problem, well, honestly speaking i don't know if AMCA can 100% take care of the J20 everytime cuz their are many many parameters to count but but if i have the choice of fighting a 5th gen enemy fighter with a 4th gen Rafale and a 5th gen AMCA than i will always choose the AMCA.
Finland and Switzerland have chosen the F35 for technical reasons, but we don't have any details. It is a matter of political choice too. But if EM discretion could be part of the decision it far to be the only technical argument.
Passive Stealth is not the absolute game changer. If currently it will give to your platform some advantages, in the case of F35 it comes with a lot of disadvantages too.
Passive Stealth will become a new standard for all newly developed airframe, because this technology is more knowed now than before, and research and development is helped with very efficient computers that simulate EM And could help you to design airframe that the first guys who have designed the first ones (F117 and B2) didn't have at this time. (it is a little bit more complicated than that but anyway...)
When you engage a combat, if your discretion performance could help you to be detected less easily by ennemies radar, it is not the only key point.
Because your steamy platform will also use Radar, because we never found a way to hide IR emission (only to limit it), and because EM discretion is efficient only face to thin band of EM scope, this advantage will not be kept as a cape of invisibility as it is often understood.
There are a lot of ways to counter "Stealth" platforms. You must know them.
If I'm a pilot of J20 or even F22 or F35, I will not be so confident in my Stealth capabilities, even in front of older airplanes. Specially if they have the ability to detect my own radar emission, my IR emission, or of they use multistatic radar detection.
In a air to air combat, Stealth could help, but it is far to be the only key point. Is true for any kind of fighter.
To answer again to
@Kalkioftoday, France is not only developing a new air frame, but what they consider as system of systems. In that "system of systems" airframe is one of the component. And some of these systems will be integrated in Rafale as well. And some of these systems will be developed as continuation that what France is already developing for future Rafale upgrades.
Don't be so confident in your AMCA.
I remind you the HAL is not able to develop a simple airframe to train your own pilots. LCA, after more than 30 years of development is still not able to perform the tasks for what it was initially developed. Navy has abandoned a carrier version. A lot of electronic is not even made in India, and the engine as well.
I'm not saying that french engineer are better that the one in India. All humans have same capabilities. But in France (USA, Russia, UK...) There is a long story behind airplane conception. These abilities are very hard to get, and then to maintain. It comes only with a very strong political will. It is what China understood and you can observe that there are spending a LOT to try to catch the level of technology we have in occident, by starting from scratch in seventies. And I personally consider that for some points there have already overtaken the western countries.
You cannot be confident in AMCA only because it will be a game changer with stealth and a lot of new technologies. For the moment it is lot of promises. If political will is strong, and development found comes also, then maybe you will have an operational fighter. But I'm quite sure it will come only with the next generation (after AMCA) because India have not demonstrate yet the ability to develop such kind of systems.
Your country need to learn a lot. They will fail and they will learn. And of they continue to spend time and money they will finish to do something well.
Consider how many time and money it took to China to be able to develop fighters, compare with the efforts allowed by your successives government's in India. There are some cultural differences for sure, but it is mainly a matter of strategical choices taken long time ago that will allow you to build an effective fighter with in the next 20 years.
All these chinese engines are reverse engineered russian engine till date! Jf17 sold to Pak with Russian engine because chinese couldn't develope a engine for that small and basic plane which doesn't fall apart every week. 
.
