Damn that’s scary. A world where no one has anything in common. I’m in my 30s and my friends and I reference songs from our childhood all the time. Shows and candy and all sorts of things.
So I wouldn't say I've explicitly made many if any friends over shared interests in music, but then once I had friends for whatever other reasons, we shared a lot of music with each other. Hardly any of them weren't "in" to music, and indeed some of them quite the opposite; they ended up in a band together (and I would occasionally incompetently noodle along with them on vocals/bass/guitar, but I wasn't remotely good enough to play out like they were).
E.D. Hirsch, Jr. wrote "Cultural Literacy" in 1987, with an update in 2002 as "The New Dictionary of Cultural Literacy". It's a huge collection of thousands of words/phrases/concepts/devices/people/places/etc, across multiple categories, that most Americans will already know the majority of their meanings, or at least find them somewhat familiar. I personally like randomly looking at the proverbs and idioms and sometimes finding parallels in other languages. It'd be interesting to go through it at random with a 7th grader and see what they've picked up -- like who says "there's more than one way to skin a cat" these days, but also who grew up in the US and doesn't understand its meaning? The book contends that about 80% of the knowledge shared by the literate has not changed for over a hundred years. Meanwhile for the 20% that changes (or is brand new) Asimov once wrote a chapter (9 in http://www.arvindguptatoys.com/arvindgupta/asimov-on-numbers...) on how so much once-common knowledge has been happily forgotten -- who needs to know about compound addition?
For the professional context, https://apps.dtic.mil/dtic/tr/fulltext/u2/a219064.pdf et al. claim you need to know 70k plus or minus 20k things in your field to be an effective expert. I think it's also why it can be easily rewarding to chat about work with colleagues, you both have a lot in common just on the basis of the shared profession.
In short, I wouldn't worry about running out of shared knowledge, nor even shared preferences and tastes, for yourself or for the world.
In practice, though, I'm sure there's quite a bit of sharing musical tastes between friend and interest groups; it wouldn't be literally everyone listening to different things.
I would wonder does increasing consumer choice ultimately erode generational identity a bit, though. So much of the "what is a boomer/gen X/millenial" is founded in what popular culture everyone was consuming in a given decade.