They do say that youth is wasted on the young.
I'm one of those older people you speak of; I was a teenager in the late 80s and early 90s. Looking back, I have to say that some of your impressions are right, but also that there's a big dose of rose-colored glasses going on.
First, regarding music and movies, remember that 90% of everything is crap. There were some absolute classic movies and a ton of great music in the 80s and 90s, but there were even more stinkers. Largely no one remembers the bad ones, unless they are enthusiasts of "le cine bad", as I call it. I was waiting tables at a fast-casual family restaurant in 1992, and used to get home late and watch "USA Up All Night", a show that presented B movies with a host that mocked them, so I saw a lot of the bad ones. Social life in high schools was disastrous; the jocks and preps vs. nerds dynamic that is played for laughs in the movies was a real thing. We didn't have school shooters yet, but bullying, including violence, was generally accepted and school authorities tended to look the other way.
As for the feeling of brightness and fun, it was certainly there, but also some of it was forced. In the 80s in the US, our president was a senile ideologue who brought us to the brink of nuclear war, we had "tornado drills" in schools in a region that was not susceptible to tornadoes (actually nuclear bombing drills), and most of us expected to die in atomic fire before we could legally drink. A lot of the media showed an idealized America as a form of Cold War propaganda, though it wasn't as blatantly detached from reality as today's, possibly because income inequality, though widening, was not as high as it is now. And quite a bit of the fun and lightness were "whistling past the graveyard". As the Soviet Union fell, some of that positivity became more heartfelt, but equally delusional, as mass culture got high on it's own supply, looking at the "end of history".
There were dark visions in the 80s and 90s though, and I should know, since I spent most of my teenage years as a goth. Horror was big in the 80s, a lot of it cheesy and surface-level, like Stephen King and slasher movies. But there was also real development of the genre from people like Clive Barker and Thomas Ligotti. A lot of New Wave music, especially in the early 80s, was a reaction to the damage being done to working-class communities by Thatcherism, especially in Scotland and northern England. The 80s also brought us cyberpunk in literature, which was fairly explicitly dystopian, and it entered into mass media by the early to mid 90s, though often with the dystopian vision weakened and replaced with just a cool aesthetic. Of course, now, we are living in the future that the cyberpunk authors imagined in the 80s, with everything coming to pass *except* the cool aesthetic.
As a side note, the trend of "darker and grittier" reboots started in the early 90s in comic books, a period that's known in retrospect as the "Dork Age". It was bad. But comic book movies carried on this "take me very seriously" style up until 2011 or 2012.
Anyway, we're here now. As you probably know, there's a pretty widespread nostalgia for the 80s and 90s right now. The Synthwave music scene is thriving, and there are mainstream artists borrowing its aesthetics. And yeah, a lot of that nostalgia and anemoia is certainly because the present is pretty bad. But the 80s and 90s were not great, and the ways in which they were bad created the conditions we live in today. I probably don't go a day without thinking about the fact that the 90s were that window of time where we had both enough knowledge of global warming to act on, and enough time to avoid severe effects, but we didn't do anything.
~bartender, if you would be so kind, take my coffee cup and bring me back a Scotch, neat, if you please.