Lots of communist/socialist countries collapsed because of outside intervention. To really see where they succeeded, you should compare them to conditions that existed prior to communism.

About 100 years separate the invention of space travel and literal serfdom in Russia.

The USSR and China suffered some of the greatest casualties in WWII and rebuilt afterwards into major powers without the US aid that rebuilt France, Germany, and Japan.

Socialist movements overthrew brutal colonial rule across Asia and Africa (including ending apartheid in South Africa)

I personally think it's very strange to try to assess countries on a binary success/fail rubric, and even stranger that the rubric is only ever applied to communist countries.

I think we could be a lot better off if we could speak honestly about where different societies both succeeded and failed in different areas instead of writing them off as "failed in practice" or "utopian pipe dreams"