The two biggest weaknesses in
Frozen are the general story-structure and the character of Elsa.
See, we are told that we have to feel sympathy for Elsa; somehow 'Let It Go' is being presented as something to applaud. But I have to ask: why? True, she didn't know how to handle her powers and she suffered for it herself, which is very tragic. But why does she let the entire kingdom suffer for it as well and then doesn't give a damn? "Okay, I just cursed the entire kingdom with eternal frost, but I just built myself a nice castle and everybody else can go f@#k themselves." Uhm... yay Elsa?
She is a totally selfish character who does nothing but bitch to every character she comes across. I know, I know, the curse, poor thing... but sympathy does stop at some point. Even people who suffer have to take responsability for their actions.
Then there's the story, which, as I remember it, is nothing more than a big going back and forth between Arendelle and Elsa's hide-out. The characters are running around a lot, while not much is really happening story-wise. It reminds me a lot of
Princess and the Frog's swamp scene, where the two frogs were traveling the wrong way simply to fill time. TP&TF had the hillbillies which were totally unnecessary,
Frozen has the snowman's song. Compare this to
Tangled's story-structure. Everything that happened in that movie, served a purpose. Everything Rapunzel and Flynn did had a good motivation and everything followed logically from what happened before. It had a tight story, whereas
Frozen is all over the place.
And that's not even counting the many plotholes and/or illogical things that are going on, like: how and why did Anna suddenly became in charge of Arendelle after Elsa fled? I don't remember Elsa abdicating? And how can the foreign merchant guy (the little old scrawny dude) order the capture of Elsa? What guard would listen to a visiting nobody who made threats against his queen? Then, how can Anna put Hans in charge while she's away? A visiting duke, rather than a prime-minister or another appointed government official? Hans, who also later has the rightful queen imprisoned? A blatant coup d'état in which everybody happily participates without questioning Hans? It's simply impossible.
What
Frozen does very well though, is presenting all of this in a way that you don't pay attention to it when you're watching the movie. You're too much involved in all the action to think over these plot points. There's too much going on to really question it at the moment. It's the strong characters and the way they deliver all that nonsense that makes you swallow it. That, in itself, is a big achievement. And I don't say that sarcastically. It's a good thing when a movie can persuade you to go along with whatever is being presented, because it means you are totally involved in it. Of course, better yet is to ot have those plot holes and have a tight story.