I never understood why they went with such design when they have proper aircraft designs to evolve. Watch the russians: they've evolved the SU models over the y

I never understood why they went with such design when they have proper aircraft designs to evolve. Watch the russians: they've evolved the SU models over the years proving that it is better than create something from 0 again. Su-27, Su-30, Su-37 all of them are far more polyvalent than the F-35 and the F-22.