It goes both ways, of course.
When people say: "Oh, we can't do socialism, or anything that looks or feels even a tiny bit like socialism, because look what happened with Lenin et al!", I think they are ironically engaging in the very essence of what lead to these attempted revolutions going so poorly.
Social and economic rigidity and dogmatism is the issue.
Socialism has some good ideas, and can be hellishly bad. Capitalism has some good ideas, and can be hellishly bad. Same for anarchism, veganism, hedonism, and so on. This isn't to say that all ideologies are equal, but that dogmatism is generally very dangerous.
However, defending the revolutions that resulted in catastrophe and complete failure is in my opinion dangerous. We don't need another trial at an extreme ideology that knows everything to guess the end result
This was not only driven by vicious men, this was there from the very start, this was inherent in the revolution and its ideology, and mainly caused by real shortages stemming from economic issues
You can see it with Lenin, Stalin, Mao and Pol Pot and i'm probably only missing more examples due to ignorance. You have an economic system which is "scientific", but is actually just a mass experiment resulting in deaths of millions. And an ideology that is so sure of itself as it is "proven" it never stops or self-questions