Both of these things are the duty of the director.
I'm not sure how any director, even a Speilberg or Scorcese can take a bad script and elevate it...
And the screenplay is indeed pretty good. A far, far better take on the material than Man of Steel, at least. But it still has to survive being shot through the Snyderprism.
Getting Goyer out of there was the best thing they could have done for this film. If they can get a different director for Justice League, they may finally have something great on their hands.
I actually can't think of a director to do something as big scale as this as well as him. However, I would want someone like Affleck taking on the directorial role with him... almost like the personal moments get handed down to him whereas Snyder handles the big epic moments. It'll never happen though.