This is a bit of a long shot but here goes.
I think this might be the novella The Crystal Ship by Joan D Vinge. Collected in The Crystal Ship ed. Robert Silverburg, 1976 and Eyes of Amber and Other Stories by Joan D Vinge, 1979 (which is where I read it).
From Eyes of Amber on goodreads
'The Crystal Ship', inspired by The Doors song of the same name, is another meeting between human and alien cultures, only this time a fully developed one with a significant back history. A colony of humans have become all but extinct, those that remain are addicted to a native narcotic and orbit suspended above the planet in the Crystal Ship, 'the dream world where all griefs were forgotten'. Then a woman named Tarawassie breaks out of her lassitude, forming a symbiotic relationship with one of the 'Real People' from whom she learns many secrets.
From The Crystal Ship, also on goodreads
The first story (The Crystal Ship, Joan Vinge) is an interesting tale of the meeting of a decadent star-spanning human civilization with a furry, collective native race—but the native race's special ability to commune with their neighbors and their ancestors, rather than helping them, causes them to refuse any change or progress and stick to huddling in drafty tents in the cold, fighting among themselves. Their special ability has become an evolutionary dead end. Just as the human "Starmen's" addiction to fantasy has killed theirs.
From my own, hazy recollection. The human's were dying out, lost in their dreams. There was still a human city on the planet's surface, abandoned but being maintained by machines. There had been some conflict with the natives in the past and the natives were not well disposed towards the humans. The marsupial-like natives (I'm sure pouches were involved somewhere) could share memories between themselves and also with humans.
A human woman, Tarawassie, goes down to the abandoned city and eventually meets up with Moon Shadow, one of the natives. Against all custom, Moon Shadow helps Tarawassie and they share memories.
I think that time-travel played a part in the story, but it was a minor detail if I recall correctly.
There is a broken (or incomplete) portal connecting the planet to the rest of the human star-faring civilisation. Tarawassie goes through, presumably to get help. The risk is that if the portal cannot be repaired then she will have to return by starship at sub light speeds, taking years or decades.
A final note says Moon Shadow never sees her again. He is shunned by the other natives and never shared his memory again.
In the afterword the author mentions that she made the ending too subtle. The story is told in the first person from both protagonists perspective. That is supposed to imply that Tarawassie made it back, managed a reconciliation with the natives, and shared her memories and Moon Shadows.