Leaping the Uncanny Valley
The uncanny valley is most certainly is involved. It is caused by a great multitude of factors, and a very important single factor that I can point you to is subsurface scattering, which is performed on the mesh. Without this, you have no hope of breaking out of the uncanny valley. Humans simply cannot be fooled when it comes to such detail, unless they have bad vision.
CGI Emily doing something the real Emily did not do is not the point here. Motion capture is about getting past the barrier of having to model a fully realistic muscular and skeletal system, so in that particular area the uncanny valley in the sense of movement and articulation is solved. The kind of advancement that you are referring to accomplish this will not come until a muscular system and skeletal structure are fully modeled. Oh, and you can't forget about skin either.. quite complex.