A number of other details: Before they died they got stronger for a couple hours, it was called the betterment I think. Having children was very important, rape didn't exist as a concept. It was a matriarchal society at the beginning of the book. It's implied it was a thing that was released that was meant to make people stronger but it failed and killed all adults instead. At the end of the book it's revealed that there are some old guys who are immortal or something. Some people had like powers, the protagonist is female and has a connection with electricity. There is a while where they inhabit a theme park, which is a patriarchal society. There are cannibal tribes which normally fight, but have instead began to unite under one leader.

I've been looking for this book for years, I first read it back in 2015 or so. I was convinced it was a fever dream until I was talking about book with a friend and they brought it up, but they forgot the name as well. Thanks!