I think this was an area for which the writer simply wasn't as well informed. Titanium and steel are both capable of fulfilling the requirements, but titanium i

I think this was an area for which the writer simply wasn't as well informed. Titanium and steel are both capable of fulfilling the requirements, but titanium is very difficult to work with. (Lockheed had particular trouble with it as well.) It's more ideal to use because its so much lighter, and increasing weight is the bane of any aircraft's existence. The Soviets would have preferred this, but they couldn't overcome the machining challenges, especially not in the scale required to build the numbers required. So they went with the safer, if less ideal alternative. And since the Soviet system did not exactly encourage discussion of shortcomings, and the "simple is better" tradition fits well, its not far to see how the "steel is better" explanation became the accepted one. All that being said, I point out that the plane did what they set out to do, and regardless of whatever compromises had to be made, it was an aerospace achievement.