I think that fantasy and sci-fi as genres both often face the tension of "what is explicitly possible due to the established laws of the author's world" vs "what we're just going to let pass because it's fantasy."
In a book or series that puts particular effort and focus into world-building, the evolution and establishment of different types of creatures, cultural groups, and races is often a part of the story, and it serves to better explain the fictional universe. This is absolutely not any type of justification for a book in which every character is euro-centric. But it does help explain the grievances that consumers have when a world with specific limitations on travel and cultural fusion (pre-industrialized, we'll say) features isolated villages with a set of characters that look like a college brochure.
That being said, I would be interested in more examples of this type of reaction for an actual book series rather than an Amazon or Netflix adaptation, because I imagine you're mostly referencing the latter.