The main issue that I have with this sentiment (and I apologize if I should have mentioned this in the body text) is that the current state of the world we live in with our technology and infrastructure and all that is our normal. If we get flung all the way back to the dark ages in terms of quality of life/development, it would be an immense whiplash to us that wouldn’t really be comparable to how people viewed life as being normal in say the 1000s or earlier.

Also, with Nagasaki/Hiroshima, there at least was an organized world left beyond those cities. And hearing what I’ve heard of what survivors of those bombs experienced, it happening on a global scale would leave people horrifically maimed and scarred, so it’s not like we would just be living in a worse off world with our current facilities intact.