If you mean societal shift in terms of accepting online dating, that happened a long time ago. But I think in your age range what you're talking about is access

If you mean societal shift in terms of accepting online dating, that happened a long time ago. But I think in your age range what you're talking about is access. College-educated 20-somethings are largely single and spend a lot of time around single people. As people get older or more rural the market thins out and serendipity needs a little help. On the other hand, for people who are finding they just don't meet enough single people naturally, I do recommend approaches like Meetup vs direct dating sites, for all the reasons you mentioned plus you immediately get past all the awkward artificial BS that happens on dating sites. And I don't mean the singles groups on Meetup, just do something fun that might interest the opposite sex. We married with children types (at least young children) don't have much time for that sort of thing anyway and the attendance will naturally skew towards singles.