Historical accuracy. I am a costume designer as a hobby. I mostly just do fairy tales. Occasionally Shakespeare. I don't do requests or make money, I just do it for myself. So, I have learned a lot about fashion, especially from the 13th century to the 19th century. Not everything, I really am still a novice, but I know enough for some things like I can tell you, Beauty and the Beast 2017 was not very historically accurate for Belle. Yes, everyone else was pretty historically accurate, but not Belle. She wore bloomers under her hiked up skirt, which did not exist at the time. The rest of her blue outfit was still fairly historically accurate, but it had the pockets on the outside (which I liked anyway, lol). Her other outfits were mostly accurate...but that yellow dress? Oh no, man, oh no! The sleeves missing was definitely inaccurate. The layered overskirts on the sides of her underskirt were totally inaccurate. And it looked bad. Now, the yellow gold gown in the animated film? Yes, it was inaccurate, but it could be said to be a rather accurate 19th century ball gown.
Here's what Belle's ball gown could have looked like for the live-action film, which was set in the 18th century, which this picture is from:

Here is my idea for Belle's yellow gold gown:

Anyway, I am sad you say historical accuracy has no place in a fantasy land. Remember, in the animated Beauty and the Beast, they say, "After all miss, this is France!" You have got to have some believability in a fantasy land to make the magic seem more special. And if the land is completely fantasy and not based on anything, you don't buy it. Snow White's collar and sleeves are actually based on Renaissance fashion, so that's some historical accuracy, there. Now remember, I said based on, because Snow White's sleeves are half accurate, they just need to be longer. I know you think these all took place "in a far away land", but as a kid I always took that to just mean a place far away from where I lived, and it could still have happened somewhere in Europe. I think I have argued well why there needs to be some historical accuracy in fairy tales. There just needs to be a balance. Certain things historically accurate, others not.
I would like Disney to do something like this:

Snow White's hair still looks short, but it's historically accurate long and just put in a net.
I also would love even more something like this:

I didn't make the left picture, but I did add the white parts to the right one. I don't like the primary color look on Snow White, but the golden skirt and sleeves do look good and make a reference to the coffin of gold and glass she gets put in. I do love the red in her sleeves and hair. It calls back to her lips red as the rose and the apple. I like the blue because it reminds me of snow, you know, wintery, but it also just looks really good. Blue almost always looks good. And then, I thought white would be a better color for Snow White's skirt, because she's Snow WHITE, lol, but Disney will never stray from the original colors. Still, I made my white version.