Yup, that's why it's such a big ask. Making a movie or TV show that works is an extraordinarily difficult thing to pull off. There are so many things that can go wrong, from the studio, to the script, to the director and actors & crew. If anything is off on any one of those levels, you've got something that doesn't really work.
The Green Lantern movie is a perfect example of that. I have no doubt that Warner Bros. was 100% supportive of that movie, as evidenced by the enormous budget it was given, but because the producers and director weren't on the same page, the final product came out lacking.