no coincidently, USA has most of best scientists from all over the world ...
Chinese scientists still not good enough to independently research without need of spying or stealing researches from more developed countries ...
the US is ahead sure, but then it had 150 years of wealth and stability at home (last war on us mainland was the civil war) while china only really had stability since the end of the cultural revolution. and only really had the money starting the the mid 90's. when you are so far behind, "spying or stealing" is a damn good strategy.
but as far as whether Chinese scientists are "good enough", china actually is extremely good in design and theory, even in the 70s and 80s its fighter designs, if realized, would have been some of the best on earth. of course industrial, financial reality was different and most never made it to prototype, many that was eventually produced had to have its ambitions scaled back and even then they were often late to service (best example, rocketry and the long march series). but what you see now being put into service is the results of decades of work and in the last 20 years china has come within ballpark of american equipment in many areas, from destroyers to fighters to data-links. this simply couldn't happen if it all relied on stealing and spying. and all the spying in the world cant help if your industrial capabilities aren't up to it. for instance if Somalia got the full blue prints to the F-22 tomorrow, it still isnt going to be able to make F-22 copies. and today the chinese military doesnt really have too much of a financial problem, nor industrial problem. it merely needs times for catch up, and catching up it is doing. consider, in 1991 when YF-22 (which becomes the F-22) was chosen to be america's next premier fighter, china had just started to field J-7E in numbers. in 2014, while the US is slowing cranking up the production of the f-35, china is flying what many are saying is the pre-production version of the J-20. in 2030 the 6th gen race could very well be tied.
ps: some people argue that the chinese system simply cannot produce world leading industries/scientists, that is simply not true, the soviet union led in many fields, the communist form of government is very good at excelling in selected fields(and being not so good at others), while western system excels more evenly across the board, china is reforming it education system in an attempt to do well across the board but retaining capability to truly excel at selected fields.
TL;DR: spying and stealing? of course, if i were the leader that's what i would do too, but that does not mean domestic scientists are somehow incapable especially when considering the fact the one country has had 150 years of prosperity and the other only started to really compete in the last 20 years
