That's not specifically about the young not knowing their cultural references anymore, though. People complaining about their offspring in general is as old as time. Although, ironically, a surprising amount of quotes about that aren't sourced properly or dubious in general.
Well, you asked for it.
O tempora, o mores has become a common use Latin phrase (Cicero, 63 or maybe 70 BC)
https://en.wikipedia.org/wiki/O_tempora_o_mores!