I don't think cultural works need to be perfect or super amazing to be popular. I think what happens to some degree is that the work resonates with a substantial amount of people, those initial people hype it up, and then others enjoy it a lot not simply because it is popular. Now let me clarify, I don't mean that they secretly dislike it, and only pretend to like it to fit in. What I mean by "like it because it is popular" is that sometimes we do like things because there's some social energy (for lack of a better term) surrounding it. I don't know if any of you have experienced it, but I've definitely had my enjoyment of a game enhanced by the fact that other people enjoy it and are vocal about it. A tiny tiny glimpse of being apart of something bigger than you, because you and several other thousands of humans are enjoying the same thing. Idk how to describe it. But "hype" might be the word I'm looking for.
Frozen probably owes a lot of its popularity to hype, but I don't think that's really a bad thing. It isn't an awful movie, and for some the themes it covers resonate enough to make it a great movie.