I didn't say you were wrong about the Russians relying design copies (there are some well-established industrial espionage cases). I just pointed out that there are other explanations as to why jet aircraft look similar. If the vast majority of your design criteria are same, the mathematics takes over.
The Russian aircraft indusry's chief customer at the moment is foreign countries. It is these customers that are driving the current evolution of Russian aircraft -- and they want designs that are competitive with western aircraft.
Fair enough.