Even with an engine, getting something to display on the screen the way you want it is not always trivial. There will be many instances where someone with programming knowledge is required to make the graphics display correctly. These people may be called graphics programmers in the credits (graphics programmer is not a certified or protected title, and the difference between different titles can vary a lot by company).
Let's bring a concrete example. We need an animated rotating circle, as follows:
Some of our options are:
1 Put the circle on the billboard, write a script to rotate the billboard.
2 Use an animated gif as the source.
3 Do the whole thing in a shader, which allows 2 different options:
- Rotate the billboard in the vertex shader
- Draw the rotating circle in the fragment shader based on current time.
In 1. someone needs to write that script, which is some kind of programming task that has to do with graphics. For 2. we don't need a programmer, unless the engine - like most - doesn't support import of animated gifs, in which case somebody needs to program that part. In 3. someone has to program the shader, which could be an artist or a programmer.