They progressed into the ability to comfortably and competent handle the loads. They stop better, they sway less, the frame flexes less, the turning radius is tighter, the engine doesn't have to scream at 5k rpm because it took a granny gear and a 4.88+ rearend to get things moving. The shocks are properly tuned for the heavier loads.
But the majority of this is not true
for trucks. We are talking "tow pigs" here. Yes, there are plastic things and infotainment systems. But my 265k mile 2012 F250 is a great example of how durable the darn things are.
Tow 15k pounds regularly with your TH400 even at 50mph, and you are probably gonna burn up the engine, tranny, and Dana 60 rearend. The new trucks are capable of pulling 25-30k pounds, funneling through 1000ft-lbs instead of 350ft-lbs, and doing it reliably for 300-400k miles (and even then, these failures are often a byproduct of the emission systems, not the "real" mechanicals). I'm not talking about the infotainment systems, I'm talking mechanical components. Dana 110 or 135 rearends instead of Dana 70 on the heavy duallies is just one example. 15"+ diameter rotors with 2 or 3 times the swept area and 4 pistons on each caliper instead of 1 on your TH400 equipped 3/4 and 1 ton trucks. Thicker axle tubes, thicker, taller frames, etc. Pretty much every HD light duty truck
has to run at least an 18" wheel to fit the rotors these days. 2.5" or even 3" receiver hitches. Massive amounts of surface area on the radiators and intercoolers and oil coolers and tranny coolers. And yes, all that leads to complexity that can lead to more problems, but the increases in quality control have made tremendous progress for reliability. Even for the electrical and electronic crap.