It's all because of Nolan and WB being impatient
No doubt that Nolan's Dark Knight trilogy are awesome. He distanced the movies from Raimi's Spider-man by turning Batman into serious superhero set in the "real" world. And WB think it's still a good formula to make DCEU as dark and serious as possible. While at the same time Marvel especially under Disney making MCU super fun and enjoyable. And then WB wanted to jump-start to chase MCU with BvS and JL, that should have been the ultimate movies equal to Marvel's The Avenger. That is why the results are horrible.
Why didn't WB start DCEU by making individual movie one hero at the time? Like that Wonder Woman movie which is good. And reintroduce Batman just like what Marvel-Sony did with Spider-Man in Homecoming, we don't have to see Bruce parents's death again like we don't have to see Uncle Ben's death again.
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Sorry English is my 3rd language