Yeah, it was the actors fault that the films were so poorly received!
WB just think they can emulate the success of the MCU without putting in the effort. Marvel made 5 films before teaming their heroes up for the first time.
It doesn't matter how many movies come before a team-up if you fundamentally don't understand or care who the characters are. Snyder doesn't understand Superman, or is outright disinterested in him judging by how both BvS and MoS seemingly don't show any desire to explore him as a person. His perspective, his wants, his reasonings... the movies have plenty to say
about him, but seemingly never from his own mouth.
There is plenty of merit to Batman standing in for humanity's anger in the face of an all-powerful alien. Less so when him outright murdering goons is never challenged, his personal history and supposed descent is barely explored, and every time he kills someone just feels so distasteful. But by Justice League, he feels like a fundamentally different person. Not someone who is redeemed, but just a completely different guy who they try to make all charming and jokey.
WW atleast got a movie where she felt like a superhero.
There is no shortage of ensemble films with a half-dozen central characters. Hell, Aquaman, Flash, and even Cyborg are barely above ''supporting" roles. But when they are so shoddily written, they could have a dozen movies before Justice League and it wouldn't matter. Because there was no true vision over this universe, and the one who was supposedly kick-starting it all was the same guy who said his Batman movie would include Bruce getting raped in prison, and thought superheroes were shit because nobody was fucking or killing each other.