Every now and then a car comes along that's so good at doing its job that it defies all logic—and the 2020 Genesis G90 is one such car. The G90 knows what it is—a plush, cossetting luxo-barge—and it sticks true to that mission. The ride is flawlessly smooth, it is competent but not thrilling in the twisties, and its two engines—a twin-turbo V-6 or a non-turbo V-8—both go about their business with nary a grumble nor a twitch penetrating the cabin. The fact that it starts $20,000 less than key riv