If you accept that your goals cannot be accomplished, why maintain them as goals? If you know it is futile, why bother? It is literally a waste of time at that point.
That said, I personally dont think it is futile. I think it mostly is an attainable goal, minus the withering of the state; I don’t think we could reach a point where the state is completely unnecessary, so I advocate Socialism. I just also think it is ridiculous that someone would try and claim something is futile while simultaneously advocating that everyone adhere to that thing. Their philosophy states clearly attainable, objective goals. If they think it is unrealistic for anyone to ever achieve those goals, then they don’t believe in their own philosophy. That is textbook cognitive dissonance.