Personally, I find it a bit of a moot discussion. As much as there’s probable and proven contributing factors to any event, the underlying truth is that history happened they way it did, because it did. The further up the chain you go the wider the net of contributing factors you need to draw from, the more it becomes little more than guess work in my eyes.
I don’t think it’s unreasonable to offer a scenario where, if Germany was literally fighting no-one but the Soviets, that they stood a decent chance a winning. Perhaps offering such a scenario does downplay the inherent strength of the Soviet state, but in a game that’s about three separate factions, there’s also zero point in offering a scenario that completely invalidates one of those factions (the allies).
They were there, they were fighting, so it’s difficult to out-right dismiss them as being entirely irrelevant to the Eastern Front. And besides, if you don’t buff Germany as being able to take on one faction on its own, you then make them completely irrelevant to the game instead.