Photo by Universal When Steven Spielberg began his wartime comedy 1941 with a visual gag in which a swimmer is ambushed by a menace from the deep (it turns out to be a submarine rather than a shark), the act of self-homage felt premature as well as indulgent. Jaws had opened four years earlier in 1975, and Spielberg’s career was scarcely much older than that. Surely no one would begrudge him the references to his own back catalogue in The Fabelmans, his 34th film as well as only the third of his movies on which he has taken a writing...