Classic in the genre of “No True Scotsman”. A fallacy.
The Right: “Socialism never works”.
The Left: “TRUE Socialism has never been tried”.
This is unfalsifiable. No matter which of the many countries have tried some version of communism or socialism, the answer will always be “it wasn’t the true version”.
Marxism claims to be scientific. But science requires that a hypothesis be falsifiable.
IMO, the best evidence against socialism are the two split states: East and West Germany until 1989. North and South Korea up until today. In both cases, one people. Divided into a capitalist side and a Socialist side. We know what happened.
One can easily find a satellite image of the Korean Peninsula taken at night. It’s pretty revealing.