I'll add some more examples so it's more clear why I think there's patterns. Also not all of these examples are necessarily bad writing, but I do think they show a reluctance to kill characters the players and writers are more attached to, for better or worse.
The Guy Nobody Cared About
- Papalymo debatably counts? AFAIK he was one of the less popular Scions, and for whatever reason it seems like the writers decided he and Yda were the weakest link. Unless I'm misremembering, Lyse only mentioned him, like, maybe twice in 4.0? Her family was a lot more relevant.
- Speaking of Stormblood, Conrad was a character who pretty much only existed to promote Lyse. At least that's how it felt when I played it. Half of 4.0 being in Othard didn't help.
- Until 7.3 Geode was just... there. The moment he said he was coming back I knew something was up, and him randomly saying his backstory further solidfied my suspicions. His death wasn't particularly relevant to the rest of the patch other than when we drank with Oblivion. But who knows? We still have his aether, so maybe they'll readdress it.
The Woman
- When Moenbryda comes up it almost always has to do with Urianger. I get why that is but he wasn't the only Scion she was close to. Weren't she and Yda like sisters?
- Ysayle had the misfortune of dying right after Haurchefant, and because of that she's often forgotten by comparison. Occasionally she's mentioned when Alphinaud or Estinien remember her, plus that one bit of fanservice in the Aitiascope. Ryne mentioned her but it was in passing. She didn't even get a portrait like the Heavensward guys.
- Yotsuyu's a villain but she also counts because of her connection to Gosetsu. I'm not gonna argue whether or not she should've died but they should've done more with the trafficking storyline afterwards. I don't understand why Endwalker's ranged quests just went back to "Yotsuyu scary" and didn't do something about the other women and girls being abused. As things are right now, her story and Doma's are unresolved without that.
- Minfilia was already heavily disliked (undeserved IMO) by the time the writers sealed her fate, which probably had something to do with the decision. I like Thancred and Ryne's arcs but I don't like how she was basically reduced to a plot device to make them happen. If she had more of a presence in Shadowbringers I might feel differently.