I personally disagree with this, mainly because a Germany led by anyone who wasn't Hitler wouldn't have started ww2 at all nor attack the USSR without a very good reason, so I see it "No Hitler=no ww2".
TBF I honestly do think if literally anybody else had been in charge of Germany during WW2 other than Mustache Man and his fan club(Doesn’t really matter Von Scheliher, Thalmann, My pet rabbit, Kaiser Willies half rotting corpse) , than Uncle Joe would have been fucking toast.
Also should be mentioned that the USSR was a entirely different beast from the Russian Empire and the reason they got their assess kicked so much during the start of Barbarossa was due to them being caught off guard during a massive expansion and reforming program meaning the units the Germans faced were green recruits and the actual veteran troops being too few. If we consider a no Hitler scenario, the USSR won't feel too secure with it's non aggression pact it had with nazi Germany and instead will look to defend their territory better against what they see as hostility from nearly all their neighbors, meaning any potential invader would be dealing with a much more prepared USSR, meaning that their winning chances go from "low" to nearly zero