We would, I think, agree that Margaret St. Clair is one of the (late) pulp era greats. Here is her autobiographical essay published in Fantastic Adventures (Ray Palmer ed.) in November 1946 to accompany her first published science fiction story: “A Rocket to Limbo.”
There are a few notable things here, I think:
First, notice she tells us rather matter-of-factly how she discovered SF via Stockton when she was nine or ten, and began digging in, including the Gernsback publications. This tells us a bit about who exactly was reading SFF in the 1920s, and it’s not quite the demographic we were led to believe – even in the “hard core” crowd surrounding Gernsback’s Electrical Experimenter magazine.
Second, this quote:
“It was an interesting thing to watch science fiction and fantasy fiction grow from the “battle between worlds” them to the current “human interest” type of story. Really, I’m glad it has taken this trend, because it seems to me that a story about people – their problems, emotions, triumphs, and failures, is a far more interesting story to read”
It’s curious she seems not to register Weird Tales and Argosy, which were very much not “battle between worlds” venues, even though she was obviously aware of them. However, more importantly note how her position on F&SF is at odds with Campbell’s.
Third, this quote:
“I first tried my hand at detective and mystery stories, and even the so called “quality” stories. I had some success with these types and my work has appeared in detective and quality magazines. But there always seemed to be something lacking, as far as I was concerned […] Unlike most pulp writers, I have no special ambitions to make the pages of the big slick magazines. I feel that the pulps at their best touch a genuine folk tradition and have a balladic quality which the slicks lack.”
So it would seem that even in the 30s and 40s “literary magazines” were developing a reputation for being a bit sere and unaffecting, while St. Clair found herself preferring the pulps as being earthier – even with the reputation she later developed for having a cynical flair at odds with the optimistic derring-do image of the run-of-the-mill adventure tales.
Meanwhile, she was already talking about the evolution of SFF from being shallow idea pieces into human stories. I think she was doing a disservice to the major authors she presumably was reading in the pages of Argosy and Weird Tales, or perhaps just misremembering them, but I have to say she seems to have had her finger on the pulse: great stories are about people. They may feature weird, fantastic locales or flashy high technology but stories that are just about that tend not to be very compelling.
But there’s another dimension to what she says here too: yes stories are about people, but they’re about people in relatable ways. When the writer works too hard to embed the characters in an artful matrix of allusion and atmosphere it leaches the life out of them and ironically makes it harder to care. Because stories are also about action.
Not necessarily action in the form of a car chase or a duel, but dynamic action on the part of the protagonists.
Sadly, something that many authors forget – to the detriment of their writing. The writing may well be beautiful and skillfully executed, but there’s this focus on atmosphere rather than events, an almost oppressive need to give the reader every detail of the setting, to describe it with a thesaurus on hand – and worse, to do it in a way that leads to a kind of plot paralysis. The characters end up doing nothing.
Want a rocket to limbo? That kind of writing is it.
 The full issue is viewable here: https://archive.org/details/Fantastic_Adventures_v08n05_1946-11_cape1736
 At least, that’s what I think she’s referring to with “Electrical Something” – the timing is right.
 Note the division already – we tend to blame Campbell, but this makes me think the idea of a division was already well established by the time he took over at Astounding.
 She’s credited for a fan letter in Weird Tales June 1934 for example…
 Heh, take that detective fiction! But indeed, one of her earlier sales that I could track down was The Perfectionist which she sold to Mystery Book Magazine, a so-called “quality” publication that got good reviews yet mysteriously had trouble making a living – so much trouble it went bimonthly after a year and a half, and then to a pulp quarterly format 2 years after that, and then folded in 1951 after only 5 years.