I think most people have declining passions as they age. Not interests... but passions. For love, sex, money, answers to all the big questions.
As you get older, you settle a bit more. Relax. Maybe even become a bit complacent. The fire smolders but doesn't burn as hot. Not all the time, or with all things, or with all people. But maybe as a general trend.
And I think those passions are what fuels the drives and the creativity. Therefore, though I've never given it too much thought, I think I'd agree that creativity comes easier to those who are younger.
With me, I consider my work more craft than art... and some of that "spark" might have lessened in that I've solved many shooting situations already. Been there, done that, know what worked to do it again next time.
