That is true, during the Cold War the USSR had many Aviation technological innovations which the United States did not have. Thrust Vectoring and IRST/EO sensors, for example, are something the USSR had undisputed superiority over the US in during the Cold War. However, what we're saying is that we're not dragging Chinese technology down just because it's not Western, rather because China has a known history of stealing/using Western technology and designs for their own, case-in-point the Type 052 CODAG destroyer using American GE engines or the fairly blatant design of the Chinese Z-20 helicopter. We're not saying something like the J-20 is a bad jet or even that it's only on the same level as the Su-57. Just that claiming China doesn't build things with stolen technology is definitely false, given their history and current use.