David duChemin hits the nail on the head with this one:
“Sometimes a photograph is a means to say, ‘Look at this!’ and other times a means to say, 'Look at me!’ I’ve got too many of the latter and not enough of the former. The ones made for the latter will always be forgettable.”
I would add, it’s more difficult to make a timeless photograph if the subject isn’t time-sensitive. “Look at this!” starts there, but a photographer like David is likely to throw in even better prerequisites.