I think we are more sensitive to these issues because there's less excuses (even 'traffic was bad' is less and less an excuse as we get ETAs, it needs to be something really bad happening to get sympathy).
We are more used to things being in sync (pre-checking shop opening hours or having average wait times for instance) and moving generally fast.
On your downtime, you would go to one of those locations and join the group already there, or loiter a little while until someone you knew showed up. If nobody showed up, you'd drift to one of the other locations and do the same thing. One out of 20 times you'd go home without seeing anybody that you were interested in hanging out with.
That's how a commons works, I think. The problem is a lack of a commons, and a suspicion of people in public who aren't currently in the process of shopping. The idea that in this alienated time I'd go to a particular restaurant where people go, drink coffee and just wait for somebody to show up that wanted to hang out almost sounds utopian or suspiciously foreign, but it was my life from probably age 12 to 24.
People who never flake out now gets a lot of respect from me since they respect my time.
This isn't unique, I grew up on the cusp of cellphone ubiquity, and I think it's that in the first few years after people have real latitude in managing their own time, there's a steep learning curve. In In my experience though, this started to change around 18/19 when people started to realize that being flakey isn't cool. Does it seem like that's happening/happened with your peer group?