Same guy who wrote Fantastic Four story also wrote those movies
No offense, but it feels like you're kinda selecting movies to fit a narrative. He was also credited as a screenwriter for Days of Future Past. Sherlock Holmes wasn't bad and Mr. and Mrs. Smith is pretty well-liked, as well.
James Gunn was credited as a screenwriter for the awfully-rated Scooby Doo movies, as well. Some of the screenwriters listed for the first Iron Man are "responsible" for writing Cowboys & Aliens and Punisher: War Zone.
"Screenwriter" credit is tricky, because it doesn't always mean what you wrote is what was put on the screen. Screenwriters, more than the rest of the production team, unfairly get the shaft, because their work is frequently at the mercy of a producer, star, director, etc. saying "I want to change that because it's MY vision" or whatever other reason.
EDIT: Beaten, wonderfully.