At one time, the Cadillac XTS was going to be GM's luxury flagship. Goalposts move, the C-suite changes, and today, the XTS is a full-size luxury car with an inordinate appeal to airport shuttles and car-hailing services. It's been supplanted as the uber-Caddy by the CT6, but that doesn't make the XTS obsolete before its time. In any of its four...
