Regardless of what he says, Spielberg doesn’t make movies about the future, he makes fantasies about the present. In the prognostication department, none of his movies have “aged well”, nor have they needed to. They were escapist classics of their time, imprinting themselves on enough of the people who saw them when they came out to cement him as part of their relative youth.
Cline was one of those imprinted upon. He took that nostalgia and Gen-X disenchantment that life didn’t turn out to be a fairy tale, and he whipped up a competently written indulgence that combined the two. Almost every human who reaches middle age winds up feeling disillusioned as their waning hormones and life’s repeated disappointments deprive them of their youthful exuberance. If you can speak to that disappointment while simultaneously looking backward through rose-tinted glasses to their halcyon days, when they were blissfully unaware that most of their dreams for a better tomorrow would be crushed, you inherit an audience through which most people have been rotating since the first cave-man despaired at the ravages of time.
TL;DR ~ RP1 works as nostalgic fan service to a very specific solid age demographic. If you weren’t some flavor of geek or nerd in the 80’s/early 90’s, you’re much less likely to appreciate it. It’s not a book about the future - I don’t know if Spielberg really believes that, you’d think he’d have learned futurism is chicanery by now - it’s a book about middle-aged nostalgia in the present. If that doesn’t sound fun, then you may not be the target audience.
Personally, I came to it with low expectations and had a bit of popcorn fun, like listening to an old mixtape. I don’t recommend expecting more from it than that.