Right now I'm reading/rereading the Steve Englehart/Sal Buscema Captain America comics from the early 70s. This was the creative team that was writing and drawing the series when I first discovered it (and comics in general). Steve was wise enough to give the book a good supporting cast, lure readers in with some high concept ideas and keep changing things up without losing focus on what was important to the book.
Steve Englehart wrote about his work on his blog:
CAPTAIN AMERICA was my third Marvel series. It was being considered for cancellation when I got it, because it had no reason for existence. Stan Lee had written it for years, and it was clearly his least favorite book; the stories had become not only lackluster but repetitive. Gary Friedrich had picked it up a year before and done some interesting stuff, but he hadn't stayed long; then Gerry Conway did two issues as a stopgap; and then I got it. The problem across the board at Marvel was that this was the 70s - prime anti-war years - and here was a guy with a flag on his chest who was supposed to represent what most people distrusted. No one knew what to do with him.
Me, I had been honorably discharged from the Army two years earlier as a conscientious objector - but I was supposed to also be a writer. So I did something for the first time that marked everything I've written since. I said, "Okay, if this guy existed, who would he be?" Not "Who am I?", but "Who is Captain America?"
Six months later, the wayward book slouching toward cancellation was Marvel's Number One title, and I seemed to have found my career. I'd also found an artist, Sal Buscema, who could draw exactly what I envisioned, so it was all good.
I don't know if Captain America was really Stan's least favorite book. (I'm saving his final run on the book to read later, so I have something special to look forward to.) It's possible. Iconic characters that represent our ideals can present signifcant creative challenges. Look at how DC has struggled to get people to buy Wonder Woman, a character who has to represent feminist ideals, and who therefore can't struggle with all the character defects and mistakes in judgement that make a character feel real. Stan solved this problem to a degree by making Captain America a man out of time, out of touch with the very nation he represented. As the years rolled on though, Cap naturally adjusted to the present era, and keeping him interesting while still being an idealized American soldier had to be a challenge for those who wrote the comic.