I have a beautiful Enterprise 3d model (which I did not build), and I think even I can light it better than that cgi one above. But then again, I don't call myself an artist.
Go for it! In the professional world, CGI artists usually specialize, just as live action production people do. There are specialists who build models, "rig" models, texture models, light scenes, animate objects and cameras and so on. While one artist may do more than one job, it is common for bigger productions to have specialists at each stage of the "pipeline."
While it may be hard to nail down any one "most important" artist, lighting is certainly high on that list. How one lights a scene may depend on the rendering engine used. CGI artists can actually do many things real world DPs cannot do—such as apply "negative" lighting.
If CGI lighting directors have so much control, why don't more CGI shots look better?
"Better" is a subjective term, and lighting is an art. Older rendering engines may require the lighting director to know more about the physical behavior of light and demand more work to emulate it. Newer rendering engines may emulate the behavior of light more realistically, and thus require the artist to unlearn
old habits and learn how real world DPs do their lighting. Andrew Price mentions this in his excellent "Introduction to the Cycles Rendering Engine
." (I recommend all of Andrew's tutorial videos, even if one is not using Blender.)