It's dim because they have to send the light thru two polarization filters. One at the projector and one in front of each eye.

The second problem is depth of field in the camera systems. The 3d parallax effect leaves you feeling that you can actually focus on items that are out of focus.

Lastly the director uses a lot of fast cuts to imply action. There is a good part of the movie that all you see are glimpses of the action and never get a chance to really look at the scenes.