I think you have to approach the setting from a slightly different perspective than you would with, say, a D&D setting, where you want to know what everything means, what the rules are for everything etc. As for players who weren't born in the 80s, I don't see it as a problem, since the setting has much more to do with the way the 80s appear in movies and tv (whether made in the 80s, like Goonies or Back to the Future, or just set there, like Stranger Things) than with what things were really like back then. The book lists lots of movies, music, even music videos to get yourself into the 80s spirit, which for me is way more important than creating a perfectly real 80s setting.
As to bits of the setting that aren't fleshed out, I think it's great to have that much room to maneuver. The kids themselves aren't likely to know very much about robots, magnetrine ships, etc. - they know those things exist, but they're mysterious. The system itself doesn't really require people to come up with rules in advance anyway, since NPCs don't roll dice or really even have stats, they just have the occasional quality. So you just have to think, ok, what is this robot for? It's a military combat robot, so it has Military Hardware 3, meaning any attempt to fight it directly or damage it outright will need 3 successes - that's as far as the stats for npcs ever go.
And in terms of places that aren't described - for me this comes back to the rule about everyday life being boring. If it's just a normal place from everyday life, it doesn't need much fleshing out, because it's supposed to be just like everywhere else. If it's connected to a Mystery, then you'll want the freedom to invent the interesting details for yourself.
I think once you start connecting things like the simplicity of the rules and the numerous story hooks throughout the book to the vague references to places, technology, and so forth, you'll find you've got all you need to dive right into playing the game. Or at least that's been my experience!