It sounds bad to say it out loud, but MAD was the policy that kept the longest peace among great powers (ie nation states that can project power beyond their borders) in recorded history. The global rate of interstate conflict has been historically low since 1945. I don't like it, but there it is.

It's also worth keeping this in some historical perspective. This war could break a long streak of zero great power wars (depending on definitions and reactions in the west), it's true. But the rate is still historically extremely low. The systems we have for peace, however imperfect, are definitely working.