Why do animated CG characters always feel fake? Why do animated CG characters always feel fake?

Usually if a CG character is an animal (or humanoid creature), they tend too look kinda off. Their movement tends to look oddly smooth or lightweight, even if aided with motion capture. Compare to real human or animal movement which is jagged, and has slight irregularity or weight. It doesn't matter whether the texture looks photorealistic, the movement of CG characters always feels off.

I'm guessing it's because the animation curves for the final images are smoothed out or simplified, like smoothing a bezier curve or something. Is that the case? Is absolute, true-to-life movement possible for CG characters?
Because animators haven't fully bridged the uncanny valley. 

There are a ton of little details you notice subconsciously that hasn't been fully mapped out.

Things like how muscles and tendons move under the surface, how clothing and hair behaves as you move around. Even how you adjust your stance as you move your arms around, prepare to move, etc.

Even with mocap it is difficult to capture and recreate all that. It is also not trivial to capture the movement of the fingers.