But my issue is still exactly the same as mono-to-fake-stereo conversions.

In 3D filming, you use two lenses to record two images, and the perspective is different in each image, thus creating the stereoscopic 3D effect.

In 2D-to-3D conversion, you have to create the second image, as only one was ever recorded. Therefore, you're creating something that was never there to begin with, much like fake stereo, or 120/240Hz TVs.

So, if I go to see a movie that was shot in 3D, in 3D, then I'm seeing a left-eye and right-eye image that were both recorded on set as separate images.

But when I go to see a movie that was converted from 2D into 3D, only one of my eyes is seeing something that was actually recorded that way. My other eye is seeing a computer-created version of the image that attempts to juggle everything in the frame around to give the illusion that it was recorded from a different perspective than it was.

You can't get real depth that way - you can't see a little bit more of the cheek behind Han's nose, or a little bit more of his ear, thus making his head look like it truly has depth. No matter how good it is, it's still going to be unnatural.