I think what kills the spark isn't age, but rather comfort, compromise, and repetition
Like, I reckon this is true in most creative disciplines that have a sufficiently high technical execution barrier (like, as opposed to just writing words on paper). When they're young, composers often write to reach, there is urgency, they're trying to solve a problem, prove something, or map an emotional state that still feels raw. The stakes are high because their identity, income, and purpose are still in flux
But as soon as they succeed, once they are the guy who wrote that thing, there's a silent incentive flip. Risk becomes optional and challenge becomes nostalgia
Like, technical growth doesn't help if there's no longer anything you're super eager to say. You can get better at painting, but if you're just painting better versions of what you already made 20 years ago, there's only refinement, no forward edge
And in music, the result is music that's usually cleaner, but emptier and less alive
There are exceptions, but these are exceptions because they still have something to solve. But most don't, most creatives are no longer trying to find the spark, they're just clumsily trying to recreate it