Should the worst imaginable scenario actually occur, after the die-off, those remaining will still have lifetimes of modern-made materials in which to re-purpose to meet their needs. It will require a lot of adaptation on the part of the survivors, but the children born after the event will likely have an easier time of it considering that way of life will be all they have ever known.
There is an article on ZH today that touches on the global energy situation that I found interesting with regard to a fossil fuel resource that is dwindling much more than TPTB are telling. https://www.zerohedge.com/news/2019-05-11/world-america-youre-fired. It touches on other issues as well that will/could/might impact the ability of the “developed” societies to continue as they are.