"Nostalgia" annoys me sometimes. Bad or mediocre times can seem great in retrospect. But aspects of culture that remain interesting aren't interesting because of nostalgia. Many tastes I've acquired might seem nostalgic, until you realize I'm also this way about times well before I was born, and it isn't about thinking life was better in those days.
There can be a component of deeply evocative familiarity. For the usual example, many people feel their mother's or grandmother's version of a dish is the best ever, just in terms of how they experience it. I've had many good spaghetti bologneses, but the way my dad makes it with two unusual twists (the presence of a "secret ingredient" is such a standard part of the story though!) just seems far better. To me, that's how bolognese should be, and it feels a lot like nobody else gets it right. And traditional Czech cooking the way I know it from my mom, aunt, and grandmother is just the same: no one else gets it right, and there's no other food like it.
There are four things going on, actually, not just "nostalgia" (one of the below is most accurately called that):
1) If people loved a thing back then, it appealed to human minds and hearts and probably still has the same emotional potentials, even though it might take some digging under the surface or into that culture.
2) We sometimes do feel that things were better in some golden past, whether or not we were actually having a good time then.
3) Familiarity from deep pathways, the deer paths we carve out in our own lives, makes some experiences especially resonant later, not least because meaning is created by time and experience and reflection and sharing.
4) Art is supposed to be evocative to begin with, its call-sign unique feelings and patterns (no one will ever write quite like Jane Austen again, etc), and when it loses something for new audiences—either by comparison, or because old references and values and languages are lost—it retains intellectual interest as an artifact of that time, place, and people, and often for obvious and extensive influences on newer work.
I hate it when people pronounce "nostalgia!" and dismiss all that in one breath because they believe cynicism makes them worldly.
Nostalgia means 2, often mixed with and easily confused with generous heapings of 3.
I have no interest in going back and living in the early 1920s, but I've never seen another movie that feels just like a good screening of the remastered Nosferatu. That isn't nostalgia at all. I wasn't alive then, nor did I watch silent movies as a kid. Its appeal has nothing of 2 and only as much of 3 as any other art that resonates with me through ambient ideas and patterns.