Director Mark Anthony Green’s “Opus” is an ambitious but uneven satirical horror-thriller that bites off more than it can chew. Centered on a young journalist named Ariel (Ayo Edebiri) who is invited to the secluded desert compound of a legendary pop star (John Malkovich) long thought to be missing, the film attempts to explore themes of celebrity worship, journalistic ethics, and the cult of fame. Unfortunately, despite its lofty aspirations, it never fully delivers on its big ideas. The cast is terrific, and their hard work keeps everything from sinking completely. Edebiri is so relatable...