I agree that MAD is likely to prevent a smaller conflict from breaking out, but in my belief that benefit is outweighed by the risk of throwing humanity back to the stone age. Given the long history of government frickups I wouldn't trust my own life to them, much less so the lives of billions to some third-world nuclear capable shithole like Pakistan, because under MAD any mistake or incident, even one caused by incompetence rather than evil intent can be interpreted as an act of aggression

And while I just stated that MAD does prevent conflict on paper, it is impossible to quantify how much of an effect it really has. We still have proxy wars like Syria and Ukraine, because both sides know that the other won't engage nuclear weapons for a cause this petty or insignificant. So we can observe that it doesn't prevent this kind of conflict, despite the fact that they are large enough to permanently frick up a country and ruin millions of lives. You bring up world wars and how we haven't had anything this destructive for 80 years, but I would argue that predominantly this is not due to MAD but due to development of global trade and communication technologies. It is simply not profitable to go to war when the supply chains span and intertwine all the world. Global communications allow you to have operations essentially everywhere on earth, thus if you want to achieve something it is now much easier to talk or buy or apply political pressure. Even without nuclear weapons we would not be going to war with each other now over political threats or disagreements because there are other much cheaper and more effective ways that countries can 'send a message' and hurt each other.