(Sigh.) one more thing we men are to blame for!
The worst part, though, is that you’re right. They’re also not designed for young boys. Or even all men.
It really is about keeping the load as close to your center of gravity, side to side and front to back. When I’m helping someone figure out their pack scheme, that’s my first priority (keeping stuff I use during the day in the outside pockets and stuff I only need in camp in the main compartment is my only other guideline.)
I almost always find that water bottles on the waist (or low side pockets) is a good start for anyone. (Hydration systems, which I don’t like, have to go where the maker puts them; this is usually OK since they put them close to the back; they don’t always put them low, though.)
The I have them load the pack using the method that has worked best for me over the years: sleeping bag on bottom, inflatable pad on top of the bag close to the back, kitchen and food on top of the pad, tent poles down the inside corner close to the back (and on the opposite side from the water bottle if you only carry one), with tent and clothes filling the space around the outside of the pack. The shove-it pocket (way out back) gets maps and toilet paper and (as the hike progresses) any sweater or jacket I take off - and nothing else because it’s too far from the center of gravity. Small items go in the lid or low side pockets or waist belt pockets. I’ll make some “guesstimated” adjustments as I go, depending on the person’s height and body type. (This is often putting a layer of clothes on top of the sleeping bag for a taller person, or putting the sleeping pad on top of the food bag for a shorter person. It might also be loading the tent or pad vertically to balance weight side to side.)
Then I have the person put the pack on, and adjust the straps (and recheck the torso length and shoulder strap wrap), tightening the load lifters and sternum last. Then, man or woman or kid, I ask if the pack feels like it’s pulling them backwards, and where the pull feels like it’s coming from. Depending on the answer, we start moving things around and sometimes re-shaping it (put the food in a tall, narrow stuff sack or in two sacks) and then put it back on to see how the fit changed. Eventually, we get it dialed in.
That seems to work better than the one-way-fits-all diagrams we all are familiar with.