When I talked about I-4 billboards before, it wasn't a hypothetical.
This is new as of the last year, and is currently rotating alongside their Epic Universe HTTYD, Mario, and Frankenstein promos; as well as some JP T-Rex and JW Raptors, Shrek and Trolls, and Minions of course. None of these are small, niche properties; and just about all of them have had some new movie release within the last 5 years, besides Frankenstein.
People might not know Brody, Amity, Quint; maybe they haven't seen the film, or would find it boring; but they know that John Williams theme. They know the Dorsal fin sticking out of the water, and that poster art. They know the Shark, and to stay out of the water when it's near. It's iconic, it's recognizable, it's exciting, and it's specifically
Universal. That's a huge win, especially for an IP that's been dormant since before the 90s.
BTTF and E.T. are similar, as neither have been capitalized on with sequels, spin-offs, reboots like Jurassic, Shrek, Minions. They've remained iconic despite that gap in relevance; and I don't think it's just nostalgia. I don't think people get "nostalgic" when a film references the Psycho theme during a tense or violent moment; or uses 2001: A Space Odyssey "Also Sprach Zarathustra" to show something grand and incredible, or when they quote Shakespeare in the script of a modern movie. It's all just a part of the American cultural tapestry. When you think of a Shark song, it's either Baby Shark or it's "Da Dum". When you think of a generic horror monster, you think of Universal's version of Frankenstein. Any flexible use of the word "Nostalgia" doesn't have to play a part at all, so long as the IP still speaks to the Cultural zeitgeist as powerfully as these properties have.