A good back system will use the hip belt to support roughly 80% to 90% of the weight of the pack, with perhaps no more than 20% of the weight taken on your shoulders. Its much more comfortable, less likely to hurt your back,and of course transfers the weight lower down, so is less top heavy. The sort of very basic waist belt that you find on surplus army packs or cheap rucksacks really does not do that. And not being adjustable for back length makes it even less effective.as long as the waist band is at the right height and all is snug I find no issue, so what in your mind is the problem and what do other packs do better? from what I have noted of more modern thinking is the frames are more akin to a cradle and more hugging with hammock like straping and padding spreading load over the back more?
Just try lifting the same load for a couple of miles with a surplus 65L pack, and one with a decent back system set up properly, and the difference is very apparent.
There are certainly all sorts of padding systems, torsion systems, etc as well, but the adjustable back system, which will adjust to your back size, thus making the waist/hip belt sit in the right position with regard to your shoulders etc is the main way to transfer load. Those other straps and stabilisers are also important, and again, make life much more comfortable.
You might have a good back now, but its easy to damage it, and there is no need to spend much money making life easier (although Osprey are not cheap, but they are popular for good reasons). The civilian market certainly thinks that way, which is why such a setup will be standard.
There is a good guide here, and somewhere like Cotswolds will show you some of their stock, and put weights in a pack to get the setup right.