INDIANAPOLIS — One of my favorite car magazines essentially called GM’s all-new full-size SUVs losers because they’re apparently not that great on the skid pad. In other words, their grip when being driven like a race car is not good. Well, newsflash, full-size SUVs weighing 5,677 lbs. and packing the underpinnings to rise up and bound over rough trails are rarely very good at autocrossing. Climb aboard the completely redesigned 2021 GMC Yukon AT4 and I suspect you won’t care.