Somewhere along the line it became received wisdom that kids won't watch anything more than a couple of years old. I really started noticing this when it came to the new Lion King "live-action" movie. There were people saying things like "Now I can finally show my my kids The Lion King, since they'd never watch the ancient original!" I just thought, why? That's just a bit older than Robin Hood was when I watched it as a kid, and I liked that movie just fine. Hell, I had seen Lady and the Tramp before that, which was about 35 years old when I watched it. Getting outside of animation, I enjoyed The Wizard of Oz as a kid (who wouldn't?) and that was over 50 years old when I saw it.
It's not like the time frame has to be on the level of decades either. Even the Christopher Nolan Batman movies are considered to be "dated" (at least in terms of interest for young people), despite the last one only coming out about a decade ago. Yet in the mid 90's the Star Wars movies were still extremely popular among children, despite having a simliar gap in time. The reason that the Special Edition movies were a big deal for kids was not that the kids had never seen them before. They had, several times, probably both on TV and on VHS. But they had never seen them on the big screen before (and keep in mind that the CRT TVs for most household would have maxed out at around 24 inches or so.) No one said "this movie is too old, I can't watch it!"
At some point there was a cultural shift. I suspect that it happened around the turn of the millennium. I base my guess on a few things:
Anecdotally I am seeing this pattern reverse someone in today's younger people, say those who are currently teens and younger. Certainly many of them are interested in old video games. A 13 year old recently broke a record for the original tetris, and I don't think this was random. I have seen plenty of young people interested in things like the original Super Mario Bros or Doom, or The Ocarina of Time. Plop a SNES classic in front of a modern kid and they will enjoy it, but I don't think the same would be true if you put a SNES in front of a kid in 2005 or so. When it comes to movies and television there is definitely more of a focus on the modern, but it seems like once young people start getting into classic cinema then they will keep looking for more classics. When it comes to books, I don't know. The truth is that most people don't read at all, so whether they would prefer new books or old books is largely irrelevant.
Hopefully this means that we are seeing a turnaround in the practices of young people, where they actually do dip into all eras of entertainment. It would be a waste if they didn't, with how easily available classics are compared to previous eras. But even with this change in behavior, the attitude doesn't seem to have changed at all. When you see a Zoomer do something like watch Hitchcock movies, or play classic adventure games, or watch Fawlty Towers or whatever the Zoomer will go on and on about how it is amazing that entertainment could be so good back then, or how this work must be "ahead of its time," or how the Zoomer himself is probably a weirdo for liking this stuff. That is, even when finding quality in past entertainment, the Zoomer still accepts the narrative that this is unusual or wrong. Society is thus still pushing the narrative very hard.