Regardless of one's view on Stalin, I don't think it's accurate to say he destroyed democracy within the Soviet Union. The Soviets, both during Stalin and after Stalin (and before) had a form of democracy called "Soviet Democracy." It was focused on electing delegates to serve at higher councils, called "Soviets." See this graphic for how it functioned:

Also read Soviet Democracy by Pat Sloan if you are further interested.

The early USSR policies built strong socialists foundations, without a highly developed industry to produce material wealth there is no possibility of a socialist future, only of an abundance of povery.

This "destroyed any hope of a socialist democracy" comes from the mislead idealists that wanted the "war communism" implemented during the civil war to continue, which would've lead to a catastrophe of gargantuan proportions a couple of decades later with the invasion of Nazi Germany.