In a simple way of saying, you brought it to copy. You can't innovate when you copy, that's why despite being manufacturing powerhouse you can't innovate any new technologies. You can only improvise existing technologies. Reinvent the wheel and you might get somewhere. Or go the legal way of acquiring the tech with hard money.China bought SU-35 with severals purposes:
-Use it as benchmark to current J11s, J15, J16...family to assess our current strength and Weakness
-Use it to evaluate our current design and manufacturing technology compare to the technology in Su-35 so we can
further improve our J-xx Flanker family.
-Study the concept of high maneuverability of the Su-35 with vector thrust
-Study the 3D Nozzle engine
-Get familiar with Su-35 so when our neighbor get Su-35, we will know how to counter it.
-study the armament package that come with the deal so we can learn more about Russia missiles.
Consider 2+ billions as our school fee to learn more about the latest Sukoi design is worth, it will certainly help China to leap frog some domain such high maneuverability with China has never charted in this domain. China is walking out the philosophy of merely copy to innovation so sign the IP with Russia is not a big deal.
Are you saying the 5th generation fighter is not as capable as the Su-35?
And India is not buying Su-35's. It's only slightly better than MKI's having Israeli EW suits and targetting pods with french navs.