I think what was really going on was, I had only a few ways to connect, and a small community, and that defined the pool of people I could draw from when making a connection, which in turn created the false impression that everyone around me connected in the same way.
Here's an intersting example: I have a Ren & Stimpy shirt from the 90's, and last weekend I wore it out to Fenton's in Oakland. While I was standing in the ice cream line a 6'2" black man in his mid 40's approached me and said, "I used to watch that show with my daughter! My favorite part was when Ren went crazy for his bar of soap!" So of course, being a total ham, I acted out part of the scene, complete with mock screaming. We connected over that one piece of pop culture, over MTV and cartoons and "quality time".
I used to think, "the only reason we could do that is because MTV was, like, everywhere. Everybody had a chance to see Ren & Stimpy, and some of us liked it." But it just wasn't true. A huge swath of "my generation" was raised in households where MTV was banned, and plenty more were raised without cable television. And if it wasn't true then, it sure isn't now: MTV has passed into history. It's been off the cultural radar for years, for almost everyone. So why did that guy and I really connect? Because the sheer unlikelihood of it made it interesting.
And how is that different from culture today? It isn't!
The only thing that's changed for me, between then and now, is now I'm aware of all the ways I could connect, and the people I could connect with, if I had the interest or the bandwidth to pursue them. In fact I'm more than aware of them, I'm inundated with them. I have to constantly fight off new channels of information, new events, even new ideas. My phone pokes me, my inbox pokes me, Yahoo and Google poke me. It's especially vexing for my personality: If I'm not careful I get distracted by shiny new things, because I'm used to an environment where I need to dig to find them and collect and curate them. Now I need to dig my way OUT.
My point is, "common culture" was an illusion back in the day, and it's just as much of an illusion today. We still bond over what we like, and we still struggle to find those things and those people.
I remember being in high school and thinking, with a combination of rage and pride, that everything on television was insipid crap, encouraging bland sameness and groupthink. My go-to image of the counterculture I embraced was a doc marten kicking in a television screen. Am I supposed to be upset that we "won" that battle against sameness, through indirect means? The modern era may have promised ease-of-connection but it only delivers it in appearance, not substance. That's okay. So we haven't transcended our finicky human nature via technology - it doesn't mean we have to go back to eating paste and listening to Walter Cronkite just to find people to relate to. It just means that it still takes effort.
What did we all have in common back then, really? I mean, ALL of us? The list is pretty short, and even the big items are questionable: We all considered ourselves Americans. (But some of us embraced the government and some of us reviled it.) We all watched Saturday morning cartoons (except for those of us that couldn't.) We all either hated or loved Britney Spears (except for those of us that didn't care either way or didn't notice.) We all read a short list of "classic" novels in school (except for first-generation immigrants, or dropouts, or kids who just had to work.) We all ate fast-food (again, exceptions)...
Seems like any net that would encompass us all is full of holes. No change there. What happened is this: We grew up and noticed all the stuff beyond our own borders. The internet sure makes that a lot easier - gives people the chance to push those borders at an earlier age - but they're still people. They plant stakes and find an identity over time. It was a complete fluke that a lot of modern culture got cut from geek cloth; I think it happened mostly because a lot of geeks got rich and that turned them into tastemakers for a while, and back in the day if you were on the internet, you were also guaranteed to know how to operate a computer. Too many other people crowding in? Boring people? Forkboys and prudes making noise? How did we deal with this in the past? Oh yeah. We ignored them and deliberately narrowed our interactions.
How is this different from what we do today? Is isn't!
"Relevance" is all about what concerns you, not what concerns others. Embrace the fact that there is more information created every half-second than you could sift through in your entire lifetime, some of it pretty great. You're not "old" if you can't consume it all. You've just been around long enough to acquire tastes. :D
Oops, this went way overboard! I apologize. I should be writing code...