The focus on sisterhood and rejection of Prince Charming are also firsts in a Disney movie, I believe.
Okay, possibly being a tad unfair with earlier comments - as mentioned I did enjoy the movie, just didn't think about it too hard maybe!
The feisty heroine bit had certainly been done before in Mulan, but I guess she in a way had a "Prince Charming". I haven't seen all of them. Nothing beats The Jungle Book for me!
Lilo and Stitch did the sister dynamic before, and Brave was also about the relation between two female family members, albeit a mother and daughter.
Even the rejection of Prince Charming and critique of Love at first sight was done before in Enchanted
(Just compare this clip to Elsa/Hans meeting!).
The only thing that Frozen did first for a Disney movie was making the identity of the villain a surprise, and even then it feels like an afterthought tacked on at the last minute.
In my opinion, Frozen is like Cars, but for girls.
My main beef with current Disney movies is simply that I wish they would go back to 2D animation, or at least animation with more of a 2D look. Ever since Tarzan and its Deep Canvas system, and then later with the Meander system used in "Paperman", they've had tools to do really nice painterly stuff that allows them to put hand-painted/drawn things into a 3D scene (though I didn't think "Feast" worked very well: basically just looked like cel-shaded 3D), but all feature movies have this cheap videogamey 3D look. I had hoped Moana would be 2D, since the Polynesian setting lends itself beautifully to more loosely painted backgrounds. Ah well.
Yes, it's a real shame you don't see many 2D movies being produced anymore, I remember growing up watching Disney and Don Bluth movies over and over again, I felt they looked like picture-books given life and they inspired me to draw things myself.
Most of the 3D movies just feel like they all look the same as well, there isn't really any big differences in style, only in budget and technology.
However, there is a good animated film of H.C Andersens tale
The Snow Queen, made in Soviet Russia in 1957. It's 2D animated and stays pretty accurate to the original story as well.
Here is a link for the curious: