As someone who shoots both types of cameras, I would suggest that is not correct. Both types of cameras can produce brilliant images and can turn out pure garbage. The skill of the photographer is paramount to creating a good image, regardless of the type of camera used. Part of the skill is understanding one's own limitations and the limitations of the equipment that is being used.
I will also say that my success rate when shooting in marginal conditions is far higher when I use my DSLR than my mirrorless camera. I completely attribute this to specific design features of the cameras (and lenses) as well as how the controls are laid out. If I were to suggest one camera as being more intuitive to use than the other, it would be the DSLR, but that is again related to the physical layout of the controls and basic ergonomics; the larger body size allowed the camera designers more options when designing the body and this allowed them to create a more flexible and intuitive camera.