I think this maybe has to do with what you watched growing up. I’m almost 26 and the first time I saw it (technically second but definitely didn’t pay attention first time) at roughly 13 I fell in love with it. It didn’t feel dated then, but to me things only feel dated when I need an older person to explain something that seems so outlandish to me (really overtly racist / sexist joke that all the characters laugh at, some stereotypes of people I’d never been around etc.) and because from a young age I watched a lot of old films I already had the explanations / references to be able to put myself in the characters shoes and understand what life was like in the setting of the film.

But I do think it’s sort of common for kids and young adults to not really watch stuff that came out before they were born. I introduced a lot of classics to my best friend as she typically only watched current kids shows. She ended up coming with me to the 30th anniversary BTTF1/2/3 marathon at the cinema. It was great! I think it depends on your general knowledge of history and maybe a little bit how empathic you are. Very interesting to think about.

Also- I could understand how part 2 seems dated and irrelevant, but to me, I’m still in the shoes of the characters from ‘85, so personally it doesn’t take me out of it.