Back in the day, plenty of screenwriters and film directors came from working-class backgrounds. Today they all have degrees from the USC film school and live in Silver Lake. They get their news from Variety and the LA Times, not drive-time radio and People. In this cocoon, the working class is something to make money from via transparently condescending TV shows, not real people with real problems.
That business about "bringing what you have into where you go" is something I've touched on before, and I used Hollywood as my original go-to example. When Tinseltown was brand spanking new, so new they didn't even have color or sound, people came into it from pretty much wherever, not just vaudeville and the stage. The idea of going to school to study any aspect of filmmaking wasn't something that would be invented for decades.
Writing seems to have had the same thing going on. If you went to school for any kind of literary vocation, it was to learn how to teach formal study of the classics. Then along came the the MFA and its conjoined twin, the prestige literary award, and suddenly literary writing was something you could study as if it were chemistry, and perhaps execute with the same theoretical degree of reproducibility.*
My long-time suspicion is that you can trace a good deal of the denaturing and desiccation of modern fiction to this phenomenon, where the function of the literary industry is to seek out people who can turn out a new version of the last flawlessly upholstered literary product about Some Important Social Issue. Albert van Nostrand, circa 1960, wrote in The Denatured Novelhow literature of the middlebrow-and-up variety was already by then being turned into a mere consumer product notable more for being readily marketable and award-ready than for its insight or its lack of dogmas.
It isn't the professionalism I decry, but the formalism, the reduction of the whole thing to a filtering and grooming mechanism — a mannered social ritual that's really more about class and signaling than it is about the development of talent or being exposed to valuable literary work.
* People like to point to the likes of David Foster Wallace as proof that the MFA thing isn't all bad, but a) in my eyes he was the exception and not the rule, and b) my own dislike of Wallace's work, for entirely different reasons, makes me hesitant to use him as an example.