... while full-blooded socialism has always, in practice, led to disaster.
That's nonsense. Those who don't want socialism to be tried, let alone to work, always wrongly conflate socialism with central planning and dictatorship rather than discussing unmolested democratic socialism. In addition, whenever democratic socialism starts up anywhere and begins to succeed, which it always does, those who want it to fail always sanction it and work behind the scenes to undermine it rather than simply competing with it in the capitalistic "market." They wouldn't dare simply compete, as they know full well they'd lose.