The "consensus on the [western] left" was the way it was because the western left (myself included) was largely ignorant of the real conditions on the ground in Ukraine and the Donbass. We were wrong because we didn't understand the situation, especially if we didn't follow Russian language media (even there it was downplayed, for political reasons) and relied on what was available in the Western information sphere which completely either misrepresented or blacked out any real information about the region. The reality is that Ukraine prior to the SMO had already amassed the largest army in Europe after Russia, and was preparing to launch an all out assault on the Donbass republics.

If they had managed to gain a foothold in the urban areas, which is a very realistic possibility given the blitzkrieg tactics that NATO trained them in, it would have been a catastrophe. What we have seen so far in the SMO has vindicated Russia's decision to launch it when it did ten times over. If the Nazis had been allowed to entrench themselves in the cities of Donetsk and Lugansk Russia would have had to level them entirely to dislodge the Ukrainian forces. Tens of thousands of civilians branded "terrorists" or "collaborators" by the Kiev regime's Nazi thugs would have been tortured and murdered. Millions would have fled, the remainder would have been used as human shields. Thanks to the SMO today Donetsk and Lugansk do not look like Bakhmut, they are not depopulated ruins, they are thriving cities.

You speak of all of the consequences of the SMO on western policy as if that was not always the plan, as if this conflict was not engineered and provoked by them precisely because they wanted to have this pretext. They left Russia no other choice and they knew it. They put Russia in a Zugzwang where they were forced to make a choice and neither choice was good. This is what nobody who says the SMO was a mistake has ever been able to answer: what choice did Russia have? What were they supposed to do instead?

They literally tried every other avenue, not just since 2014 but since NATO expansion started, they tried explaining their concerns to the West about NATO expansion time and time again, they repeatedly warned, they tried negotiating - doesn't work when the other side doesn't negotiate in good faith and only sees agreements as a ruse to buy time to rearm (as has been admitted by multiple European leaders), when the other side doesn't abide by the agreements - they even tried putting an entire draft treaty proposal in front of the Americans to avoid having to launch the SMO. Nothing worked, Ukraine was getting more and more Nazified, more and more militarized, pumped more and more full of weapons by the West. All this before the SMO, mind you.

It would have been a massive mistake not to launch the SMO. If the Donbass had been overrun and fallen to the Nazis the Russian government would have had a political crisis on their hands that might have brought down the entire government. Leaving the Ukraine situation to fester was creating an existential security risk for Russia that would have destroyed the Russian state. Instead now Russia is in a better economic and military position than it has been since 1991. NATO is panicking and increasing their budgets because they have been humiliated in the Ukraine proxy war. They really believed they could engineer a regime change or even collapse of the Russian state using this conflict, and instead it is NATO that is now close to collapse.

NATO may have (formally) expanded but in material terms it is weaker than ever, its stocks of weaponry and ammunition so depleted it will take a decade or more to refill them. If that's even possible given how this conflict has exposed the systemic inability of the privatized for-profit arms industry to keep up with the demands of a real peer conflict. And it is by no means as united as it pretends to be, we constantly see signs of their dysfunction and inability to agree on any substantive action. Throwing more money down the bottomless pit of the private MIC won't change this. It will only further destabilize the social and economic conditions here in Europe as our social safety nets get gutted, taxes increase, inflation continues to rise. Sooner or later this will cause massive political crises in Europe.

Meanwhile Russia's military industry is reinvigorated, their army expanded, reformed and massively more experienced. Their economy is thriving not despite but largely because of the sanctions and how it has forced the Russian state and economy to adjust, reorient, re-industrialize, and to clamp down on much of the neoliberal rot left over from the 90s. And diplomatically they are more popular across the global south than they have been since the days of the Soviet Union.

Was everything done perfectly? No of course not, far from it. I even think that much of this was not foreseen or planned by the Russian government, they very much were forced to improvise on the fly. Being consummate liberals, they were surprised at how hostile and how hellbent on Russia's destruction the West turned out to be (despite the fact that many in Russia, especially the communists, were trying to warn the government about this). They were very naive up to and even some time into the SMO. And even they did not expect their economy to hold up as well as it did.