> they didn't have smartphones to fiddle with in bed
This is solvable for people who want to. We have a dedicated charging station in our house for all electronic devices. Before bed, all of those devices get put there. Including me and my wife's phones.
This definitely is the way to do it. I have started keeping my phone in my living room at night instead of my bedroom, but am still bad about doing this every night. Phones are addictive and it is mentally hard to break out of the addiction. It is essentially a "you just have to do it" situation, but "just do it", while technically simple, is still difficult if you're addicted.