Lantley,
A lot of folks have probably not towed with a recent gas rig. My new to me 3014 GM 1500 with a V6 has pull three times in two months, granted not high profile trailers, but 6500 and 8000 lbs. I've only been at 0-600' elevation. Never got what I would call slowed down. Including the 8000 lb rig putting me over gcwr per say. I'm sure comparing my 05 dmax to a new one, would be night and day too.
ALL the newest trucks be them gas or diesel have improved majorly since 2014.
I did notice mpg dropped on 2020 gm 1500 models. Not sure if it's body design. Or dare I say, last DC inhabitant playing political games reducing mpg goals, along with other removals of vehicle regs.
In 14 across the board mpg and HP went up in gas rigs.
Marty