So your father is similar age to mine. It's not that they didn't see those movies. It's just they were old by the time our parents were teens and other things were "hip&cool".
If you poll people born in 80 or younger, chances are, most of them never seen that movie. At best, they saw few pics. If you ask gen Z, results would be even worse. At least our generation watched them when it came on tv cause there was nothing better.
To be fair, even iconic movies from 60-70's would get same treatment.
Also, Gygax is out of D&D picture for a looong time. Modern d&d isn't Gaygax's d&d.
Good comparison would be with isekai anime/manga. I had no idea what that was, had to google it. But it's all the rage among 20 something year olds.