Steven Oxman Taking an overly respectful and frankly miscalculated approach to its source materials — the 2003 roman à clef novel and the 2006 Meryl Streep and Anne Hathaway-starring film — the new musical version of “The Devil Wears Prada,” now trying out in Chicago ahead of a projected Broadway run, provides some serviceable entertainment but needs a hefty dose of guilty, edgy fun to boost its mild pleasures.At this stage in its development — having persevered mightily to reach its opening after enduring over 20 cases of COVID during rehearsals and previews — the show boasts an Elton John score that operates in too limited a register and a production from director Anna D. Shapiro (“August: Osage County”) that never quite decides between authentic glamor or a more theatricalized kind, resting right now in a merely semi-satisfying middle.