Like I said, I'm in a relationship. I don't go to the gym, don't drink, and never attempted to pick someone up at a store. Like finding a job, I've found the best way to meet people is by way of recommendation from people you know. Doesn't always work out - had some extremely poor experiences - but that's life.
Otherwise, I would mostly agree with your second paragraph in general. I was raised Catholic, but stopped being Catholic somewhere between 4th and 6th grade (so there may be some bias, both ways), and agree that church, sports, school, and work were typically the ways people would get to know others, and eventually hook up.
I'm not a young person, so I'm not about to know what challenges they face in an always connected world, 24/7 news cycle, and world leaders (and their speakers) using Twitter/social media platforms to communicate with each other, but that seems to be the big shift since I was. Disconnecting is great (playing board games is my go-to), but with the world placing such importance on the benefits of the Internet and all these social platforms ...
It seems as though the root of this is less socialization. I always thought you were usually supposed to get to know someone before asking out. I know HN isn't big on religion, but churches served this function among others for a long time, and I don't think the large, secular group of young people has yet found an adequate replacement. In terms of a close-knit community with similar values, religion is hard to beat.