It's not like scripts are treated like sacred texts in Hollywood. Directors have a huge impact on what finally hits the screen so while the screenwriter does deserve blame, it's not like Fleischer's hands were tied and he had to go with what was on the page. He had input and it still sucked. Given that this is the second well-regarded script that Fleischer has turned to shit, it's a knock against him.

As for Emma Stone, I doubt she was a choice that the studio forced upon him since he had worked with her before on Zombieland.