Yep, while Russia is good at engine and airframe design they are behind in terms of optics and stealth. But their are other advantages like maneuverability maintainability and cost to manufacture.

Literally all irrelevant if you get taken out in a BVR engagement by a less maneuverable plane you can't see (or by a missile coming off an F-15EX you do see, being spotted by the F-35 you don't).