There’s a scene in “Shadowlands,” the 1993 portrait of novelist C.S. Lewis, in which a young boy is excited to discover the giant wooden wardrobe that inspired “The Lion, the Witch and the Wardrobe.” He throws open the door and reaches through the coats hoping to find Narnia … only to feel cold, hard wood at the back of the armoire. Disney wouldn’t dare undermine one of its franchises with such a scene, and yet, with “Christopher Robin,” it’s made a movie that feels similarly disenchanting — the latest and least of the studio’s live-action reboots of a widely adored cartoon.

Whereas “Winnie-the-Pooh” author A.A. Milne probably would have approved of the concept behind director Marc Forster’s well-meaning spinoff, it’s hard to imagine him being especially pleased with the result, in which an enchanted reunion between the now-adult title character (Ewan McGregor) and his stuffed bear helps...