Recently shared the bttf series with my 11yo. The third doesn't hold up too well, but the first two are great. The funny part was that she saw the 80s and the 50s as basically the same.
I think it's an issue of the fact that they're both "before my time". I treat the 20s and 50s as the same, I wouldn't be able to tell you any difference, even though they must be massively different.
Yeah, they both just looked "old fashioned" to her. Obviously she could pick out some differences, but when they first went back to 1955, she didn't really notice that the cars, outfits, signage, etc. were particularly more dated than they had been in the 80s version.
Is that because neither of them have any electronic devices? They both have payphones and cars that don't look like today?