Sure it’s possible that no one has ever tried the flavor of socialism that bypasses the corruption and power-seeking all rulers have been prone to for millennia. But it is a weak argument to rely on that.
All we know is no one has proven a non-corrupt fully socialist state that actually has a good economy has been achieved. Both that and cold fusion might be someday achieved, but I think cold fusion is orders of magnitude more likely. All it takes is one bad-faith leader to bring down a political system, so even if it’s achieved it may not be worth it.
Why do I say a good economy? Because I assert that even with its flaws, it’s way nicer to be a very-low-wage earner here than even to be median in Mao’s China or modern-day DPRK. So if you have perfect equality with a worthless economy it’s not really a victory.