There are certain aspects of light which the rendering equation doesn't model, so it's insufficient for true realism (the Limitations sections of the Wikipedia

There are certain aspects of light which the rendering equation doesn't model, so it's insufficient for true realism (the Limitations sections of the Wikipedia page is a good summary). It's pretty damn close, though. I feel that the "ray tracing" vs. "path tracing" question is nit-picking for a very specialized audience at best. Most people simply understand ray tracing as being about tracing rays through geometry in some way (so both ray casting and path tracing are a form of using ray tracing). How you combine this tracing to give you pixel values is a higher-level question. If you look at ray-tracing frameworks / APIs like Optix or DXR, it's clear that this combination of tracing is left up to the programmer (for good reasons). What's important for the API to expose is the primitive operation of tracing a single ray, after all.