If you want to understand some of the raw horror from fans, I will try to simplify it.
Imagine a fantasy book series that, stories and concepts and whatever aside, went out of its way to offer sympathetic and progressive narratives regarding gender, religion, sexuality, race, and identity, in a time when doing so was neither trendy nor popular in the literature sphere.
Imagine it having done all this without dipping into dumbass proto-SJW dogma and maintaining a constant theme of "everyone is human*, for better and for worse, no matter what they look like and what they identify as" and never putting anyone on a plinth nor damning them as uniquely flawed, thus ensuring the stories never age into cringy irrelevence once such faddy demagoguery comes in and out of fashion.
Now imagine literally all of this unceremoniously thrown in the shredder, with the most generic corporate-woke schlock of currentyear shoved in its place against all logic and sanity, because those involved with the production for all their claimed progressiveness and inclusivity didnt give two shits about anything other than burying everything in wokewashing sludge that serves only to beef up their diversity credentials, and will be forgotten forever within weeks of the show finishing
*for want of a better word