> And third, in-person interaction is a network effect. If 20% of people would rather be on their phones, that reduces everyone else’s options for in-person hangouts by 20%.

That should only be a problem if you can only hang out with a fixed group. If you live in a city of five million people, it shouldn't make much of a difference if one million of them would rather be on their phones then hang out in person. That's still four million people to hang out with. The only question is how to find those people. Meetups are one way.