Downton Abbey just finished its six-season run two months ago, but if you have been fiending for British accents, period costumes, poorly managed hereditary estates, class tensions, love stories revolving around a young woman named Mary, and the nostalgic eye of Downton Abbey creator Julian Fellowes, here comes Julian Fellowes Presents Doctor Thorne. The miniseries, adapted from an Anthony Trollope novel, arrives on Amazon on Friday, having aired earlier this year in the U.K. under the simple title Doctor Thorne. For its move to America, the show has put on airs. These airs reflect Amazon’s ambitions, ones that will perhaps...