The USSR did good things and bad things but reactionaries like to pretend it was all bad. There are hard numbers about life expectancy increasing, better life for women, research achievements, general quality of life and happiness metrics, and more that increased. There was lots of bad parts, but same in the US.
There were anti gay laws on the books for the US, and towns you couldn't even walk in while black. Hell, there are still some sundown towns in places in the US. If you just point out that stuff, or if you lived in such a horrible area or had family who did spreading their stories, then it will just come off as a hell hole. The US does suck, but it's not just Skid Row, the projects, lynch mobs, coups, wars, etc. Same for the USSR. There were good things we can save and build on, and bad things we need to avoid for future socialist projects.
It's not like the first attempts for democracy went well, either. But I wouldn't diss it in the Middle Ages and say we can only do monarchies, the pinnacle of political achievements, just because " it never succeeded. It fell in Greece and the Roman Republic and every other time it's been tried, and has never worked ever and thus is always doomed to fail."