USSR was literally the first attempt at building a worker state, and it was demonstrably better than anything before it. On top of that, USSR was under the threat from the imperialist west throughout its whole existence. It was invaded by western powers in 1918, then plunged into WW2, and the Cold War right after that. Obviously, that forced the Soviet Union to develop in a way that made it possible to preserve itself. Blaming Stalinism here is frankly absurd.