The suspicion of a "mentality", if such a manifestation exists at all, is not evidence that copying occurred.
Dude I can give you thousands of example from Google Search engine to bikes, cars, apple phones -- Chinese should be given Ginese World Record certificate for that.
No, reverse engineering is exactly what you've described: difficult. The technology, subsystems, and supply chains, that differentiate the J-11X from any other Flanker, however, were not fruits of reverse engineering.
I understand, it was the Chinese need to bring the technological barrier and difference in a quick time, and Chinese used its Money and took advantage of the former USSR disintegration and gets many strategically tech. from the CARs states.
India on the other hand have the advantage of having good relationship with almost every country, and excess to the testing labs, and the OEMs which could help.
But there is a disadvantage in India, and that is the Democracy and that's why there should be no comparison of India and China. For China, setting up a plant or a Lab, is just the matter of taking decision, but in India, even to acquire a land, could lead to the Court which could takes decades.
With Reverse Engineering means understanding the technology from the complete system needs time, money and much effort, but it should not be mixed with the building the system, by IPR violation, which Russia have demanding for its IPR violation fine. And why SU-35 deal to happen took so much time, is due to the IPRs issue. As far as copying Russian Engine, or the Radar is concerned, that the time have passed, when it could be so easily copied, and in reality shows that China have agreed to pay the price, and now no other systems of the Russian claimed IPRs would be exported. Don't feed yourself too much of the Propaganda blogs written by the Chinese serving officers, or the Western articles who over estimated Chinese systems too much to create the sensation.
Chinese can replace, the subsystems with its indegenous system, but it does not make J-11X different that the SU-27 variants like SU-30XXX