Granted, this is often how Hollywood works. You have to take the work that you're offered, and while you're discouraged from inserting long monologues about the horrors of bureaucratic indifference to the common man into whatever inane Melissa McCarthy vehicle you've been slapped with, if you hang around and reliably hit your deadlines for long enough, you might get your shot at a dream project.
Perhaps the most challenging obstacle Mazin had to overcome was being Ted Cruz's roommate at Princeton. But then, even that's allowed him to build a second career out of insulting Cruz on Twitter. Hey, it's good to have a varied skill set in this economy.