The Soviet Union was, if not a traditional dictatorship, absolutely a totalitarian autocracy. Stalin was a brutal dictator and his successors were chosen by the communist party. Elections in the USSR were for show.
Life was miserable almost from the start of the Bolshevik revolution for most people. The USSR's implementation of communism was so bad, it's become cliche.
The Soviet Union wasn't a dictatorship. Read Soviet Democracy. It lasted as long as it did because it had tremendous GDP growth while lowering wealth disparity, free and high quality education and healthcare, doubled health expectancies, full employment, and over tripled literacy rates to 99.9%.