"It's not your story to tell"
With all the discourse around own voices, representation in writing etc., one sometimes hears the phrase "it's not (someone's) story to tell." Some lad writing about childbirth? Not your story to tell. A White woman writing about racism towards Black people in France? Not your story to tell.
This sometimes comes across like a yes/no binary, but I think there is a continuum here. Let's take the example of "Inferno" - a blistering memoir by Catherine Cho that deals with her experience of postpartum psychosis. This is a story from Cho's life, so clearly it's her story to tell - someone else telling it would be biography, not memoir. (By the way, in case I'm not making this clear yet, please check "Inferno" out-well worth a read).
Let's imagine: as a cishet, European man, if I were to write the story of "Inferno", about a Korean woman experiencing postpartum psychosis, and then call it autobiography, that would just be transparent charlatanism on my part. You could make the same case if I were to write it as autofiction (a fictionalised account of events that have really happened to one). One the other hand, if I were to write a work of pure fiction about a woman with a very similar experience, using ""Inferno" as research, it would be based on my second-hand understanding of someone else's lived experience. Nonetheless, the specifics of this work of pure fiction are going to be unique to each teller - so this made-up story would be my own. If someone only wants a story informed by lived experience, that's their choice, and an understandable choice at that. But it seems a bit incoherent to say a unique work of fiction is not person A's story to tell, when person B, person C and person D will all tell different stories (albeit they might use a similar frame to hang their story on).
Let's say you want to write a piece of speculative fiction. If you write a sci fi novel about a difficult pregnancy set 50, 100, 200 years into the future, you will likely be thinking of new technologies that will affect the experience of pregnancy, childbirth and postnatal care. Of course, lived experience of pregnancy in general will help to inform how one might respond to new tech. However, the more advanced the tech in your story becomes, the further the imagined experience will unmoor itself from contemporary lived experience. Notwithstanding how difficult it is to write speculative fiction that is completely divorced from life on Earth today, the more "alien" the experiences described, the more one has to project oneself into a story that bears little resemblance to any writer's real life.
However, even if we accept that every purely fictional story is each writer's own story to tell, it is understandable if people get annoyed that a story written by someone without lived experience garners widespread praise and/or makes a lot of money, while a similar story written by someone with lived experience languishes in obscurity. One doesn't have to be hyper empathic to see why this would make someone feel resentful. Sometimes this resentment can occur regardless of how much research a writer has done or how many sensitivity readers it's gone past (although it's more likely to be outright anger if the writer has done a lazy job and is getting props for it). If a novel about discrimination towards trans people written by a cis person becomes the book of the year, even if that cis writer has put in hours and hours of research and consulted with any number of people, there will always be someone who will feel that a trans person should have their book in the "top spot".
It probably doesn't help when the business of publishing can have a "winner takes all approach", where only a small handful of books have massive mainstream success. One can hear the implicit message of "sorry, this is going to be this year's big book about people with intellectual disability, it's going on the Oprah club, we're just going to talk about THIS book." I suspect a lot of the heat would be taken out of this debate if there were more books being read about the same topics, and the "midlist" were taking up more space.
It's worth asking what you're trying to do with a piece of fiction. If you're using speculative fiction to think about how changes in society in response to an imagined future technology might affect different people in different ways, there are so many ways of doing this that you're probably less likely to "steal the limelight" from someone else. On the other hand, if you're trying to save some group of people with your fiction, and it's a group you're not a member of, maybe think twice before you don that cape and try to fly.