Batman v Superman can best be described as a “beautiful mess”(Chris Stuckman). But I feel there is one thing that would've fixed a lot of problems with the problem. But for the sake of the argument let’s say you had to keep David S. Goyer, Zack Snyder or Jesse Eisenberg. We then have to look at the very end of "MAN OF STEEL" in order to find the solution. No, I’m not talking about when people seem to misremember him cheerful and willingly snapping Zod’s neck. You know the man who was literally born and bred to kill and destroy. Who has DECADES of fighting experience against someone has 0. Who was also getting more powerful as the fight went on. And Clark who’s never been in a fight in his life and has only been Superman and had full access of his powers for what 2 days! No, I’m talking about the scene right after that. Imagine if this were the same Superman as in his last appearance in Man of Steel. That Superman was confident, experienced happy. If that Superman was in Batman V Superman it would've changed the tone and dynamic of the film. People would've been more conflicted on which side to choose(Superman or Batman). The mistakes he made in the film(the government hearing, the hostage) would've been resolved in a more realistic or logical way. The Superman as a Messiah or god figure also wouldn't come into play as much and would halt the film at a time when it should be building up to something.
The main problem I had with B v S is that it was a Batman film with special guest star Superman. Clark Kent/Superman was severely underwritten and his dour appearances helped drag the film down. By regressing Superman at the start of film(Dawn of Justice) the filmmakers retconned Clark/Superman's personal development from "Man of Steel". "Man of Steel" was a coming of age film and at the end he was the Superman everyone “says” they wanted(and yet mock at the same time I don’t understand that). With what happened to Clark in "Batman V Superman" realistically he will have to go through 2 films(at least) for him to reach that point again. By that point his character is going to feel tedious.