This is an interesting question regarding James Thurber's story "The Secret Life of Walter Mitty." I personally do not regard Mitty as a stock character, and I do not view the main theme of the story as a conflict between a man and his wife--although there were certainly other stories by Thurber, such as "The Unicorn in the Garden" and "A Couple of Hamburgers," in which that is the main theme. Walter Mitty's wife may be a stock character, a henpecking wife, a backseat driver, but Mitty does not seem like a stock character and one who would be in danger of becoming obsolete because men like him would morph out of existence. There are plenty of Walter Mittys in our modern civilization, and chances are there will be more rather than fewer of them as modern civilization becomes more and more complicated.
It seems to me that "The Secret Life of Walter Mitty" is mainly about a man's retreat into a fantasy world because of his inability to cope with reality, and that the character of his wife was created for dramatic purposes. She gives him someone to talk to and to interact with. She also provides him with directions and errands which give motivation and movement to the plot. Otherwise, the story would be confined to one man's consciousness. He is not the kind of person he is because he is always being browbeaten by his domineering wife. At least, I don't see it that way. I think he would be exactly the same man whether he had a different wife or no wife at all. It is not a story about a conflict like that between Erwin Martin and Ulgine Barrows in Thurber's "The Catbird Seat." There is no great conflict between the Mittys. Whatever conflict may have existed in the past seems to have been pretty much settled in the wife's favor.
"The Secret Life of Walter Mitty" bears a strong resemblance to E. B. White's story "The Door," which is also about a neurotic man's inability to cope with modernity as represented by New York City. Thurber and White were friends and colleagues. Both worked for the New Yorker for many years and helped to shape it into the great magazine it became. They collaborated on at least one book.