When did the nature of the complaints change?
I was a lurker mostly back when the original HP film were coming out. Back then the complaints were, interestingly, focused on the film-makers not making the series ‘dark’ enough. There were demands for more gore, more violence, more dark scenes, and endless blathering about how Yates/Heyman/Kloves shied away from making the films truly as adult and dark as the books. (I don’t believe Potter fans, in general, had much experience with actual dark fantasy if they thought the books were so unflinching). But now this has been inverted: looking at a lot of peoples' issues with Fantastic Beasts and more recent complaints, people now bemoan Yates not having enough lightness in his films. They’re too dark, grim, bleak. There’s not enough whimsy. So what’s prompted this? Is it a matter of fans growing up somewhat, realising the complexities of the real world, and wanting this world to remain in the light, flighty mode?
The Potter fandoms nit-picking, however, seems to remain in tact.