We absolutely have to have survivors and that doesn't mean the ones who live, that means the ones who can fend for themselves because they may not have anyone else in their area that can/will/or you'd want to.
Remember the book The Stand by Steven King? Well, the coming micronova is going to bring that to life.
If you want to learn what to do and not do, read the book Alas Babylon. I read it in 1970 and have never forgotten it. It's a book on how to survive a nuclear war. It really stuck with me.
If your prepping, put your survival food in PLASTIC bins that have a very strong locking top. Home Depot has ones that are black with yellow lids. I have a dozen, they stack, will withstand water and plastic acts like an insulator. Put your BULLETS in plastic container too for the same reason, it's an insulator.