Children's authors and inadequacy

I'm halfway through an interesting biography of Margaret Wise Brown and I just read this article in the Times on Maurice Sendak. (And for good measure, throw in the Margo Rabb Times piece from earlier this year.) All of this has inadequacy and failure on my mind. Here's a bit from the Sendak article:

... he is plagued by the question that has repeatedly been asked about Norman Rockwell: was he a great artist or a mere illustrator?


“Mere illustrator,” he said, repeating the phrase with contempt. It’s not that Mr. Sendak, who has illustrated more than 100 books, including many he wrote, is angry that people question Rockwell’s talent; rather, he fears he has not risen above the “mere illustrator” label himself.

Similarly, Wise Brown was tormented by the sense that her work for children was not valuable and that she should strive to write for adults. (There' are long discussion of the book she worked on "with" Gertrude Stein and of her relationship with the poet and actress Michael Strange that are particularly fascinating on this point.)

I don't think this sense of writing the wrong thing or of writing in a less valuable genre is unique to children's book authors at all, but it does seem to have a unique character. (Am I correct in observing that some authors of adult "genre fiction," especially sci-fi, have a protective chip-on-the-shoulder underappreciated attitude? I am not being critical--just an observation.)

Thoughts?