My observation is if there is a "weakness" regarding load carrying, and therefore also towing, in the current generation of so called 1/2 ton trucks, it is they are somewhat softly sprung in the rear.
A guess would be the manufacturers know the vast majority of the buyers are not using these to carry loads much of the time. They are daily drivers so they get soft springs for a soft ride.
This is easily and inexpensively remedied. Also changing to better quality shocks, and adding an anti-roll bar ( if not already fitted ) is a worthwhile change. All of this can be done for less than $700.
