So to speak, getting associated or even blamed for a second Eternal September that would have happened regardless? I personally don't know. And I only use smartphones to stay in touch with family and friends, listen to music, and browse this specific website.

It wasn't the advent of smartphones as much as it was the popularization of them. Once everyone and their grandma got their mitts on an iPhone, it was downhill from there. The internet went from its experimental "we need content to draw people in with, everyone, just do whatever. have fun." phase to its "ok, now that there's people here, it's no longer about fun. let's extract as much capital as possible from everyone" phase.