I know it's not apples to apples, but I had a string of Acura TL's and TLX's with a 3.5-liter V6, and I got some of the best mileage of any cars I've ever owned with them - 38-39 mpg on the highway at 75-80 mph. Weight about the same, and a slightly larger engine.
True, they weren't turbos, but a turbo should actually do well on gas mileage if you don't stick your foot in it too much and blow gas out the exhaust. After all, a turbo makes power without having to stomp it. In fact, I get the best acceleration out of my turbo Optima with only light pressure on the pedal.
The bottom line is that 25 mpg on the highway for a 3.3-liter V6 in 2018 ain't stellar mileage by any measure. It comes down to the 3.3-liter being around for awhile and not being known for good mileage. If scoot is all you care about, that's great. But Hyundai/Kia needs to do some engineering work to make that engine a little more efficient ... or come out with a better one.