The 2020 Cadillac XT6 stakes its claim in the realm of three-row crossover SUVs, but it has its work cut out for it. The 2020 XT6 sits between the smaller, two-row XT5, and Caddy’s perennial luxury SUV bestseller, the Escalade. It arrives in Cadillac showrooms at the same time some non-luxury brands have fielded some compelling three-row...