Do folks generally still believe that the "masters" are/were born great, rather than being born with an advantage of some sort (whether by nature or environment) and then leveraging that to achieve mastery of some craft?

I do. There was nothing particularly special about Chopin's environment, yet he was cranking out brilliant, innovative works by his early teens.

I don't know about born "great" but born with a different perspective seems reasonable. The perspective maybe nurtured by the environment. I think the environment could be a repetitive task or plenty of leisure time.

I believe luck with timing is the biggest determination.

Great point.

Vonnegut comes to mind in literature. In one of his novels, he even grades his other works A-F based on how good he thinks they were. His grades seem remarkably accurate, too, given my subjectivity as a reader, and his bias as the author.

Seems like the passage of time has a role in accentuating the genius of artists

> passage of time has a role in accentuating the genius of artists

That makes sense, I think genius is time evolving process.

One pattern, I have seen in high performers, is that they are competing only with themselves, using introspective feedback to continuously improve in an ego free way.

Yes. If you come to conclusions independently and those conclusions survive positively for hundreds of years, credit is due