Dictatorships use suppression. Communism is a style of collective government. The USSR was never communist, the government merely used the lexicon of communism to suit its needs.
By this definition, has there ever been a communist country?
Pretty common though: North Korea is a democratic state (according to its name), but not real democracy. National Socialism wasn't really socialist. The UK isn't a real monarchy.
It's a language game compelled by the guilt-by-association level of political sophistication of our culture. When the debate is rarely more sophisticated than 'that's socialist, like Hitler!!!!1!', it's no wonder that the response has to be 'that wasn't true socialism'.
The big difference between National Socialists and International Socialists was that the former wished to strengthen their economy/people through careful curation of the economy and nation, whereas international socialists wished to replace private ownership everywhere (communism), and most promoted revolution as a means to that end.
I agree with you entirely that most people fall back on the 'no true scotsman' fallacy to disassociate their ideology with Hitler and the Nazis. What has always been curious to me is that people still identify with USSR socialism despite Stalin and the Soviets being equally as abhorrent as Hitler and the Nazis.
The people drawing cave paintings in Chauvet 30,000 years ago were living in a communist society. 10,000 years ago the entire world was communist. Then slave societies arose in the Middle East and elsewhere.