When the sky is dull and uniform, the easy excuse is to leave the camera in the bag. There are no dramatic clouds, no warm light, and no rich shadows to carve out shape. Everything looks like wet cardboard. But that flat, unkind light is precisely where you find out if you actually know how to see.
Golden hour is forgiving, it flatters everything it touches, disguising weak compositions with cheap warmth:
"A flat grey sky doesn't do any favours; an image has to stand entirely on structure and texture."
When light stops being the story, you have to look for form. You start noticing the harsh bite of wet shingle, or the subtle shift from dry sand to tidal sludge. It forces you to rely on contrast of material rather than contrast of light. If a shot works under an unbroken grey ceiling, it works on its own terms.