No chemistry between the characters
I think part of the reason the ST feels a bit flat is how little chemistry/connection there is between the characters. I'm thinking of this "behind the scenes" video:
https://www.youtube.com/watch?v=3WIQigWP-U4
It's like, HAN,LIKE, AND LEIA! They meshed well together, and felt like a trio. With the main three in the ST, it's a bit nothingy.