My experience with the Goonies is similar. I don’t care for it at all, but I think I was too old when it came out to enjoy it. By then I was really into Star Wars, Star Trek, Indiana Jones, and Middle Earth, and it just felt too childish for my sensibilities at that time.
I also didn’t like Back to the Future for similar reasons; it just felt like soft, half-assed sci-fi, more of a teen coming-of-age comedy that used sci-fi trappings, and made by and for people with little appreciation for the genre.
Even a few years before, I thought E.T. was a little too kiddie-flavored for me, though I mostly enjoyed it.
Interestingly enough, I just watched E.T. for the first time since I saw it in the theater on cable a month or so ago, and it really struck me how, like BTTF, it was just using science fiction window dressing to tell a story about a middle child in a broken family unit. The spaceships and aliens are really ancillary to the main story, and there’s also a ton of religious symbolism in it, too.