You are right. The author has absolutely no clue what he is writing about. Just like what you pointed out.
He also claims raytracing does not solve photorealism, but does not back this claim. No single argument why! [Edit: But he's right here, for photorealism you probably want a combination of methods, like ray tracing and radiosity or ray tracing and photon mapping]
Complexity: For raytracing, you can store the scene in very efficient data structures, so you do NOT have to search your "billions of triangles" for each ray. Also, you can make sure rays degrade quickly since you trace them from the camera backwards to the light source, as you have pointed out.
"How do you raytrace stars"? They are a light source at infinite distance. This is a solved problem in computer graphics - And a pretty simple one at that.
Materials, Physics, Content and AI have nothing to do with computer graphics AT ALL.