For me it's the complete disregard for the original material and what appears to be nothing more than a diversity-grab. I grew up reading the comics and some of the characters I'd very much look forward to translating to the big screen, instead they took various big name actors that in no way resembled the source material they were portraying.
Does it bother me enough to stop me from watching/liking the movie, ABSOLUTELY NOT. But to even see a preview and have a strong familiarity with the original content I see what's being presented and have to ask this question
They didn't change Iron man, they didn't change Captain America, they didn't change Dr. Strange, they didn't change Captain Marvel (well in the comics they have several times anyways), they didn't change Black Panther, they didn't change Guardians of the Galaxy, they didn't change Black Widow, they didn't change Thor.......did I miss any? .....They didn't change Daredevil, they didn't change Luke Cage, they didn't change Iron Fist, they didn't change Punisher
They did change the Eternals. I'm a fucking comic book nerd not a racist.