The surprise to me is not that today’s kids have their own set of favorite authors, in genre and out of it; the surprise to me is honestly that anyone else is surprised by this.And indeed, I'm not surprised by this notion, but it does represent a difference in the SF/F world. I was a teen in the 1990s and read all sorts of stuff from the 1930s-1960s corridor that generally represents the Golden Age, the same way (near as I can tell), teens in the 70s and 80s did. This is literally the first time in history when readers weren't introduced to SF/F via Golden Age authors like Asimov, Clarke, and Heinlein (as Scalzi notes, Tolkien probably still reigns in Fantasy). What has changed?
I think a big part of it might have something to do with the on-demand nature of our current media environment. To take an example from another medium, kids growing up in the 70s didn't have much choice as to what movies they watched. It was whatever was playing on TV or the local theater, and a lot of what played was in the public domain. In other words, film nerds in the 70s saw a lot of silent movies by default. I grew up in the 80s, and with the advent of cable, I didn't really see any silent movies until I started actually studying film. I did, however, watch lots of black and white movies or movies from long before I was born, simply because that's what was showing on Cinemax or whatever. You can really see the difference in film critics who grew up in an earlier era, they have a much broader base to draw from when discussing current movies. Nowadays, it's all about what's on Netflix.
Bringing it back to SF/F, I think this is a big part of it. Many folks hit up the classics of SF/F back in the day because they were basically the only thing available. Book stores had tiny SF/F sections and primarily stocked the classics with the occasional new release. These days, kids can snag an ebook or even an audio-book on-demand, and their available choices have exploded in the past couple of decades. SF/F has sorta conquered the world, and is widely available everywhere. Thus the classics, while still available, are getting dwarved by other books.
And this is before you get to all the other options kids have to occupy their attention these days (video games, anime, internet stuff, etc...) There seems to be a dismissive streak running through fandom these days. Perhaps its because there's so much new SF/F flooding the market. There's too much to keep up with; you don't have a choice but to filter in some way.
One thing a lot of people mention when it comes to this is that kids don't like the classics because they can't relate, which seems kind of silly to me. Sure, old books were written in a different context, and there's a lot of weird stuff people were exploring. But for crying out loud, this is Science Fiction we're talking about here! The whole point is to explore alien ideas and blow your mind within the confines of a rationally knowable universe. When people are pining for the Golden Age of science fiction, they're craving that Sense of Wonder we got from Asimov, Clarke, and Heinlein. Lots of great science fiction is being written these days, but a surprising amount is dystopian misery porn or boring character studies with a veneer of SF Tropes. This is especially rampant in YA fiction, which is so melancholy that I'm wondering why we're so excited by it. Maybe the reason people keep recommending Heinlein juveniles is because so much of YA fiction is dedicated to gloomy settings and grim despair. There's nothing wrong with that type of story, but is it really surprising that some of us crave Golden Age throwbacks like, say, The Martian?
I suppose the worry is that this represents another cultural battleground where kids don't read the classics because they're trying to establish a "safe space" or some other such nonsense. Again, I find that odd considering the whole point of speculative fiction is to expand your horizons. To a lot of people, reading is a passive activity, but it really isn't. If you're not interrogating what you're reading, you're doing it wrong. This gets us into strange territory though, and we'd have to go about discussing what really makes the SF genre work, which is probably better served in its own post someday.
None of this is malicious or necessarily dangerous, but it is different, and for the first time in 70ish years, kids aren't reading the "classics". One can't help but wonder what that will mean, but I'm not too worried. People like what they like. I don't like the idea of dismissing the classics out of hand, but I wouldn't be surprised or upset if someone got into SF by reading, say, Scalzi or Weir. For instance, I don't think Fantasy is anything but strengthened by the popularity of Harry Potter. The same is probably true with SF, even if I'm not a huge fan of dystopian YA...