Yeah but then it's game over. I used to worry about nukes, especially with all the suicidal people in the world, but then I realized that it's not worth worrying about because there's no way out. Anyone launches a nuke and it's game over, MAD.
Realistically, if Russia were to use nuclear weapons, they would completely lose Indian and Chinese support, the last two nuclear powers currently playing nice with them. So long as something debilitating is the consequence of nuclear weapons, Russia will abstain.