When a client says a render looks like CGI, they rarely mean the lighting solver. They mean something in the image contradicts how the eye expects a photograph to behave.
Camera height is the first tell
Architectural cameras default to somewhere around 1.6m. Renders shot from 3m read as a doll's house instantly, because no human has ever seen a room from there. Match the camera to how the space will actually be experienced.
Material scale beats material quality
A perfect oak texture tiled at the wrong scale looks worse than a mediocre one at the right scale. Check the plank width against something known — a door leaf, a light switch — before touching the shader.
Nothing real is perfectly clean
Edge wear, slight reflection variance, a rug that is not perfectly parallel to the wall. Perfect symmetry and spotless surfaces are the fastest route to the uncanny valley.
Grade it like a photograph
A raw render is a negative, not a final image. Contrast, subtle vignetting and a considered colour temperature do more for believability than another two hours of sampling.