If it makes you feel any better, modern climate and economic studies have shown that even a full scale nuclear war involving every nuclear power at the height of the Cold War and when nuclear stockpiles were far larger than today we still wouldn’t have come very close to actually killing off all the humans on earth, with the vast majority of the casualties being owed to famine in regions that were/are heavily dependent on western fertilizer. Indeed entire nations in the southern hemisphere tend to get through such senecios without much of an direct effect from world war three.
Mostly this change from earlier predictions came from being able rule out the theory of a nuclear winter as climate modeling became more accurate and we could be sure that the secondary fires from such a war could not carry ash into the upper atmosphere in significant quantities, which was practically shown when a climate change fueled wildfire in Australia got so large that it should have been able to carry the ash into the upper atmosphere under nuclear winter theory but none was observed, validating modern climate models.
Also, dispite what some less scrupulous journalists trying to drum up clicks have posted on the Ukraine War, the Russian government itself hasn’t really made any major signaling moves with regards to bringing nukes into the conflict, and indeed has maintained and repeatedly reiterated Putin’s 2010s no first use policy when asked.
Don’t get me wrong, this is not the result of some greater Russian morals or whatever, but just a consequence of the inherent risk that such posturing could lead to nuclear escalation and breaking the nuclear taboo or even just other nations actually believing they plan to, and such scenarios end very badly for Russia in general and Putin in particular.