That's bogus; you can absolutely get a nice soft ride in a 3rd gen! The 4th gen and up might have more sound deadening, but as far as actual ride, you could definitely make a 3rd gen ride comparable to a "4th gen+". Like you said though- suspension is very subjective, and up to the person's preference.
OP-
You make it sound like you want a firm ride for the trails- why is that? Generally speaking- firmer is better for on-road handling, and softer is better for off-road. That being said, you need to have your spring rates correct for the weight you're carrying. If you have lots of steel armor, you'll want a higher spring rate than if you're maintaining a mostly-stock weight.
The rear coils are super easy to swap, and I think 5th gen rear coils might be a good option for you. You can usually pick up rear 5th gen coils with super low miles on Craigslist for cheap. They're made for a slightly heavier rig, so they have a higher spring rate.
To swap rear coils, you just pull the bottom of the shocks off, pull the end links off at the frame, jack one side up, and the drooping side coil will fall out. Using that method, I had zero issue getting my tall 3.75" lift Superflex coils in.