the goal of fans who defend less-than-well-written female characters has never been to make the rest of fandom “accept” them for how a sexist creator wrote them to be (and if this seems to be the case for any one specific fan then believe me, we’re just as wary of them as you are)
we’re trying to make people stop viewing them with the same Misogyny Goggles as the writers are. yes, characters like Sally or Irene or Molly or Mary roll out half-baked because the writers couldn’t even be bothered to make them anything more than two-dimensional. but that doesn’t justify the hoards of bloggers calling them such gendered slurs as “bitch”, “slut”, etc. this is why many fans feel the need to speak of them in a more positive way.
this does not mean they are happy with how they’ve been written. you’ll find that many people in a female character’s fanbase are just as dissatisfied with the show’s faults as you are, and they choose to voice that dissatisfaction by giving said female character the characterization and story they believe she deserves, even if the writer never intended her to have them
it is easier to like or sympathize with the show’s male leads because they are better written, and it’s perfectly ok to do so. but while we may not have the power to change what poorly-written women that showrunners give us, we do have the ability to change how fandom receives them. to repeatedly call ourselves powerless is an insult to what we’re capable of as critics, writers, artists, etc.