>the entire rest of the Ghost crew gets sufficient characterization to be likeable within the first episode, Spark of Rebellion
You know, I was just thinking this.
Here is the thing? What do Ezra and Luke both have in common? When we meet them, they're weak, unskilled, and naive.
Part of having a likable cast is seeing characters grow and change. Literally all of the cast has seen this, except Sabine.
Back to my first sentence, I knew from the very first episode they had fucked Sabine up. It was the shot where she takes her helmet off, and is literally looking down at Ezra.
That tells the audience "She is above Ezra, she's trained, she's smarter, older, and stronger". What the fuck, that didn't happen with the other characters, at least not in such a ham fisted way. Hera is the mother figure who has learned to balance her personal feelings with advancing the Rebellion. Zeb was the muscle but has since proved to be much more than that, offering some spiritual elements to the show. Kanan is the mentor who had to first learn that he can prove to be a good mentor. Ezra of course is our Jedi-in-training, and is slowly progressing into a more mature and well-rounded character, with unsettling hints of him falling over the edge of the dark side.
But Sabine? That moment, in episode 1 where she looks down at Ezra without even saying anything interesting? Yeah, three seasons later, that's still her.
She's Boba Fett for little girls. "I have cool armor and I know how to shoot and blow things up, so that means you have to like me."
They literally forgot how important it is to give her some kind of story or development, because she looked cool.
Only now, in season 3, are they giving her a proper arc, with the Dark Saber. I think it's only fair that we give her (and Filoni & co.) a chance, but the sentiment that it's too late is natural.