I don't think it was so much not knowing any better, it was the expectation of the customer as well the available shocks and tires. HP Mopars got better suspension than the low perf ones, for a reason.
I would agree - it had nothing to do with "knowing better". Citroen used torsion bars and unibody construction in the 30s. Chrysler introduced them in the late 50s. So it had to do with the consumer at the time who had coils sprung full-frame GMs and Fords to choose from and the torsion bar suspension was a far better, lighter, and responsive setup. Compare that to a FWD platform from the 80s that could out-handle and out-brake even the best factory torsion bar setups. Then compare the 80s FWD to a 2015 vehicle. Even the base models of anybody can handle and stop well. My GF's Santa Fe has a front sway bar larger than I can even buy for any of my Mopars and it's got progressive springs and struts that are all improvements over the old stuff. That's what the modern car freak drives every day. Jumping from something modern to a 50 year old car comes with some acceptance that they are nothing alike in capability.
