NEW YORK — Nia DaCosta, director of the upcoming “The Marvels,” has a diagnosis for the recent struggles of superhero movies. For DaCosta, whose two previous films were the Jordan Peele-produced horror remake “Candyman” and the acclaimed 2018 indie crime drama “Little Woods,” it’s imperative that superhero movies aspire to be fresh and daring — like “Across the Spider-Verse.” “The …