I wouldn’t necessarily blame the writers for the shift. The bigwigs making the decision believe that using existing IP means that half the marketing job is already done.

I don’t blame them for the shift at all, that’s all on the higher ups who only see dollars. I do however blame them for doing things like not engaging with the source material and actively changing character personalities to fit their own idea of the story. Specially when it is so drastic that it goes against the overall story and it has to be retconned or explained in unbelivable ways.

(Yes I’m still bitter about The Witcher show)