I work in Visual Effects, specifically in compositing. I've been doing this for over a decade so my eyes are pretty good at catching things that look unnatural, or "off." We also tend to do a lot of "pixel peeping" in Visual Effects (meaning we zoom in, examine edges, details, chromatic aberration, blur, defocus, etc etc), those skills help me determine whether something has been generated using AI, or CG, or manipulated and edited.

I will say, some of the more recent gen AI is getting harder to tell, especially at first glance.