doctorbadwolf
Heretic of The Seventh Circle
She's the most well-known personage from the Shadowfell plane. As they wanted to have "lords" of the Shadowfell just like they have "lords" of the Feywild (which are the Archfey) they had to start somewhere. So they took quite possibly the most popular divine figure from 4E's setting and are now keeping her identity active in the history of the game.
Do they need to change things a bit so that she can still apply to other settings in which she is not an actual god? Sure. But so what? I'm sure all the Greyhawk players were questioning all that weird Dawn War fluff that got given to Pelor when he showed up as a god in Nerath. Or how Moradin's stories are all different in all the different settings that have used the dwarven pantheon.
We all saw Asmodeus become a god in 4E and we got over it. I think we can handle the Raven Queen not being a god in non-Nerath settings and get over that too. Because at least we still get to use her as a character in the game rather than completely wipe away her entire existence because we aren't playing 4E anymore.
The needed to change her place in settings that already have a God of Death, they didn’t need to change her fundamental nature and persona.
Asmodeus became a god, and literally nothing else about him changed. He was absolutely 100% still Asmodeus. So much so that if you play it as him having become a god very recently, as they did in 4e FR and Eberron, it isn’t disruptive at all.
Making RQ a lesser deity in settings with established gods of death would have worked much better, but more than that, she can be an Archfey (whether literally or Shadowfel equivalent) without reinventing who she is as an entity.
If you have a god is summer and one of Winter, Titania and Mabd don’t suddenly need to be changed. There can be a Fey Lady of Death that has nothing to do with the setting’s god of Death, is an ally, is an opponent who seeks out adventurers to help her stop his cults and champions, etc. She can have a seat of power that is outside the god’s grasp, perhaps given to her by gods that oppose the god of death, or stolen by her from him, where from she keeps she watches over what she isn’t strong enough to control, and sends her agents to stop the cultists of Nerull, hunt down necromancers and intelligent undead, etc.
In FR she would be an ally of Kelemvor, and a thorn in the side of Shar, who hates that she has escaped her for so long.
There are a hundred ways to handle such a character that don’t require reinventing her just to change her place in the world.