Lazy writing, meh CGI, plot and tropes you've seen hundred times over, flat characters.... I could've forgiven them all and given this movie a neutral rating if not for one thing that drew me mad.
Exoticism.
Now, if you have seen lots of Chinese costume dramas and movies you'll know 99% time the styling is not even 70% accurate to actual history which is fine, as long as you use your artistic license in a sensible and consistent manner and doesn't pretend to be what you are not.
But here, all the side characters were dressed in a way that resembles the Mongol Khan era fashion but only the female lead was dressed in a dresses that resembled Western model of "princess style" that had little to no similarity with Chinese styling. To appeal to whose palette?
To me it seemed like movie makers thought if they dressed the princess in a way that is more authentic the viewers wouldn't find it compatible with their idea of "pretty", especially viewers who are unfamiliar with C-content/only came to watch because of Dylan Sprouse.

So yeah, I was thoroughly unimpressed. Do not recommend.