Maybe, but iPods and Walkmen predate smartphones by a few decades. I recall posts from a decade or so ago from men bemoaning headphones as a blocker from interacting with strangers.
If it wasn’t phones, it’d be newspapers. People will find devices to keep to themselves in public.
Newspapers, iPods, blackberries, the modern smartphone. The effect on the mind gets progressively worse from these things. I'll often go out somewhere without my phone, but I'll bring a book or newspaper and I easily get more distracted by what's happening around me and can't focus on reading. A smartphone? The apocalypse could be happening and my mind unchecked wouldn't pull its attention away the screen.
If it wasn’t phones, it’d be newspapers. People will find devices to keep to themselves in public.