Ultimately it's not a matter of him coming to the "right" conclusion, it's whether he can answer the questions posed by material conditions. So rather than saying his conclusions are wrong, describe some of the problems the USSR faced and ask how he would have dealt with them. Both of the sources I mentioned go through this in detail, I strongly recommend them to everyone.
Regardless of your opinion on the outcomes, I don't understand how studying these revolutions "doesn't work". Should we dismiss the French revolution with no investigation?
Both the Russian and Chinese revolutions succeeded in seizing the state, defeating the armies of the bourgeoisie and aristocracy, and surviving their attempts at sabotage and terrorism. How did they do so? What can we learn from these decisions? What might we have to do differently with our different circumstances?
If you think the revolutions failed, what caused them to fail, and what specifically should the parties have done differently? And we need concrete answers to the real problems they were trying to solve, not idealist hand waving.