I think people are right that it isn't as bad as some people would have you believe. Not as a film, at least (though it is poor, considering things like editing and pacing and character development and story).
But man do I hate it. I hate it for the opportunities it spoiled (being the first Batman/Superman film, correcting Man of Steel's wrongs, to name a few). I hate it for taking iconic comic book moments and characters, and still managing to shit the bed. This is a film that took from The Dark Knight Returns, had Batman and Superman, Lex Luthor and Doomsday, and does the Death of Superman, and manages to handle all of those things poorly. It leaves "how disappointing" territory and enters "how fucking dare you", for me. How can you take those things on, all of those things, and have no understanding of what makes them work?
Maybe that helps contextualize the beating this film is getting, for some people.
Yeah, that's a good way to summarize everything.
I was skeptical about this since the beginning, because I did NOT think that TDKR, with it's psycho-miller-batman, was the right direction to go in. Partially it was because of sheer predictability. Boy, I wonder how Batman will find a way to stand up against Superman, oh it turned out to be kryptonite, who would have guessed. Similarly, I called some kind of monster coming up to be the climax as well, it was just a matter of what Lex would make. Cyborg Superman, Doomsday, Parasite, Metallo,....okay, it's Doomsday. Without ever seeing the movie, I could predict step by step what it would be, and the pieces aligned as it went along.
But more than anything, I just didn't want to see Psycho-Miller-Batman. I admitted to the open possibility that it might have been done right at the time. I think TDKR is a well written comic. But that doesn't mean I have to like it. Other than Adam West goofy Batman, the hardass, gruff, miller Batman is the least interesting Batman of them all for me. He's only badass on the most shallow, surface level, and it's always the moments of Batman struggling with humanity and pain that made him compelling to me.
And starting the movie off with Batman and Superman being antagonistic was the clearest red flag for me. The strength of Batman fighting Superman is that none of them want to fight. That's why you generally get plot devices like mind control to justify them going at it, because for the most part, they're friends, and friends fighting is far more compelling narratively than two meatheads going at it out of hate. Civil War understands this. When BvS trailers were showing, they showed Batman threating Superman with the "You will bleed" line. Civil War, on the other hand, has Cap apologizing to Tony for needing to fight, because Bucky is his friend, while Tony replies in a hurt voice "So was I." That is fucking awesome. That is actual drama. I care about their conflict because they care about each other. With BvS, especially since I know TDKR is the inspiration, their conflict would be based on meanness and insecurity and pointless anger.
But all that might have worked if they had done it right. I might have never been able to love it, but I could have atleast respected the craft of it, if it was done right. And I do, to the parts that were done right. Costumes look nice, action is nice, I like that we finally have Wonder Woman on screen. But it failed on every level that mattered. And badly.