Well I guess we just disagree on the impact of low GCVW. I will make the concession that some buyers don't care about the numbers. They will buy what they want to buy and pull what they want to pull. These are typically private individuals. However fleet buyers don't operate that way, and many HD's are bought for business. If I am fleet buyer and I am pulling or carrying heavy, if that weight is over the GM spec, GM is out of bid, end of story. If I am just under the GM spec, I can operate the GM truck near capacity but if we buy Ford or Ram I still have an additional 7-9K of capacity. The perception is that the other trucks are operating well under their capacity while the GM truck is maxed thus working harder and you could expect less life out of a truck working at its capacity than one that isn't. I think that effects sales.
I do recall the low step height. However changes to frame design have made the GM HD's as tall as the other two. Which may be why nerf bars or running boards can be ordered from GM with your pickup. I actually think a set of boards was standard on my 3500, although I deleted them. I think the current ride height look good and have more ground clearance than previous. I think that low ground clearance of previous gens actually hurt it in the HD arena. They dragged their bottom over rough terrain and they did not look as robust as Ford. That has changed and for the better, even if you have to work harder to get into the increased ride height, the GM HD's look HD, some specs speak to HD capacity (Hp and Torque) and those that don't (GCVW) will be fixed in 2020.