There's a line from U2's "The Fly" that has always resonated with me: "Every artist is a cannibal. Every poet is a thief. All kill their inspiration, then sing about their grief." And also this, from Miguel de Cervantes Saavedra: "Hunger is the best sauce in the world."
While creative types remain creative all the way through, the angst of being young, whether the initial figuring-out-of-oneself as a teen, the anguish of the first time or twelve of having your heart broken, the frustration of not having enough money to survive, or even just the desperate need to convey something you've figured out to others -- all of that tends to sharpen one's artistic output. That drive tends to fade with success, unless one learns to channel the pressure of increased expectations, from themselves and others, into that creative space.
Certainly we've talked on here about how John Williams peaked in the late '70s to roughly the late '80s, how, while he's absolutely still a competent composer and totally an engaged conductor and musician, the spark of inspiration has been falling off since. Jurassic Park was probably the last original and stirring complete score I can think of from him. He's come up with some nice themes since -- although he repeated the one he came up with for Hook in Harry Potter and Attack of the Clones (you hopefully can tell those are separate films, but god -- now I want to see Harry Potter and the Attack of the Clones), which is less than original.
My personal favorite 20th century composer/musician is Vangelis. I have a sizable chunk of his discography, though not some of the absurdly-limited-foreign-release sets, and none of the frustrating number of his film scores that have never been released. He also seems to have had his period of the most creative need through the '70s and '80s. He'd see things and be inspired and BAM! another studio album. While also working on the score for his latest Frederic Rossif wildlife film and another studio album that inspired him to create. And maybe another film score besides all that. Now he's in his 70s and creating something every few years. It's still good... It's just definitely less.
And how many pop songs, in just about any genre/language/culture, can I point to for the last century and find a theme of, at essence, somebody pining after somebody else? Many. Many many. Or its close cousin, venting about someone they had previously been pining for. And then the ones that aren't tend to be about the pain of inventing/reinventing oneself as a person and/or the perceived expectations of others. There's not that many that are "Life is great. Everything's awesome. I just paid off my credit cards. My sweetie is wonderful. I know what my life is about, and I'm comfortable and happy." Because comfortable and happy people tend not to produce Great Art™.
Ironically, comfortable and happy writers tend to be in a better position to get to the Weird Writing Place™. Maybe that's why Empire worked so well. George was under pressure and creatively dissatisfied. Leigh and Larry were established screenwriters. One had the germ of the idea. The others knew intimately and comfortably the nuts and bolts of how to string those into an engaging narrative. Maybe that's where the path to greatness lies: Hungry and comfortable meeting and collaborating, the latter providing a means, channeling the energy of the former in ways they wouldn't have been able to avail themselves of on their own? Vangelis and Ridley Scott -- BAM! Blade Runner. John Williams and Dick Donner -- BAM! Superman. Tim Burton and Danny Elfman -- BAM! Anything (but especially Batman).
I see it in the writing arena all the time with established authors teaming up with new/newer ones to assist in fleshing out their idea into a book. Maybe that's the best of both worlds in any of this... One person's comfort zone shoring up the discomfort of the other, and vice versa. I feel like the "lone auteur" is as much of an outlier as the "true self-made man". 99% of us only get anywhere good as a result of the connections we make along the way.