By the first sentence I simply mean that ascribing to a sphere of influence worldview doesn't necessitate disregarding other causes of war; saying that encroaching on Russia's sphere is an escalation that risks conflict doesn't mean that appeasement is some panacea. In fact it can't necessitate this because a sphere's power exist due to the threat of force. If Ukraine weren't under some sort of implicit or explicit threat Russia wouldn't have any influence.
So maybe the war would have happened anyway. At some point it was unavoidable, I don't think it was always so but if it wasn't I don't know how big a role the West played. I'm pretty sure it played some role, but it might have been miniscule and irrelevant, I simply don't know. The war would certainly have been different, though, very different.
I'm not saying that Ukraine would have been better off under this or that. I don't know how the different scenarios would look, I don't know their likelyhoods, and I don't know what the Ukrainians would prefer or what they would be willing to risk to achieve that. At the point the war happened Ukraine's preferences are pretty clear, though.
I still don't get the point about futility. You say that the analysis might have held under the USSR era, but it's not like it was inconceivable that the cold war could have turned hot. If that happened the spheres would likely break or move, either because the world ended or because someone came out on top.
About Mearsheimer, I don't know what sort of blame he's talking about. Is he saying that the war wouldn't have happened without the West's actions? If so then he's either right or wrong about that, but Russia's latest setbacks are hardly relevant. Is he laying the moral blame on the West? If so then that's rather spicy, but this latest grandstanding isn't solely about him, it's the "whataboutism posse in the geopolitics thread": it's about anyone questioning the narrative where the West or NATO is nothing but passive observers.
And, again, even if this supposed posse is completely wrong, why would you need to spare them a thought because of Ukraine making a breakthrough? Where has any of them expressed a wish for Russian victory? It doesn't make any sense, and in my view is just an extension of following the war like a game. It's a crowd chant, a boo, not a sentence with actual meaning. This isn't directed at you.