I dont think people realize location for ETA needs to be set to on always which will update the Apple Watch app every 30 min but if they do Idk what people are talking about honestly. Maybe they dont understand when you open the ETA Apple Watch app you need to click on the location you want then force touch on the display that says the location, traffic, address and more menus will pop up; one of them being "set as complication." It immediately showed up for me with the correct time and light indicating traffic was good. This is amazing for work.
rb1216 about ETA - GPS & maps driving times