The Darkhold feeding someone's worst angels is absolutely what its always been about, though. I don't know any incarnation of it where extended contact with it didn't wreck someone.
In fact, it is kind of important that it does. Wanda is insanely powerful. And, dramatically, that's a problem. It means there's no real challenge for her to overcome. The influence of the Darkhold provides that challenge. It shifts the movie from being about who is stronger with magic (a boring question) and shifts the questions to really be about the moral questions of what we do for what ends.