[longdog]

What are those other areas which display age-based creative decline? Other creative fields I can think of off the top of my head - scientific research, animation, fiction writing, architecture - are overwhelmingly dominated by older people.

Even in pop music, I'd argue that artists are doing very little of the actual heavy lifting compared to the producers and the writers. Pop singers have a much shorter shelf life than producer/writers due to the importance of image in appealing to younger fans. See https://en.wikipedia.org/wiki/Max_Martin for an example.

[mellosouls]

Eg. Maths, physics, poetry. All dominated by the young, as pop music.

Note that I'm talking about creative brilliance - ie the outlier contributors that define or excel in the forms - not workmanlike producers of commercial trustworthiness as in your example (though I would assume that generally the same trend holds).

I said "some" because I'm aware that some fields (eg literature) do not follow the clear example in those.