I'm going to push back on this. Seems like we've had this discussion before. One reason military gear is built extremely tough (hence extremely heavy) is because military troops often need to carry massive loads of gear. It is not uncommon for troops to carry well over 70 lb (32 kg) loads. Very few civilian hikers carry that sort of load. Military gear also often has lots of molle and other attachment points for mag pouches and other military gear, which adds weight. Most civilian hikers I see with military packs don't actually use a fraction of the molle features on their packs. But all that green molle does look tacticool! Regarding "ONLY military issue packs have straps long enough to fit extra gear under the lid. Civilian ones often are barely closable.", you need to look around more. Lots of well designed civilian packs have long straps.

In my opinion, the best compromise between weight, durability, and useful features are packs designed for technical climbing. My current favorite pack is the Black Diamond Speed 40. It's lightweight, and plenty sturdy. It has an inner sleeve so can be extended for larger loads. The straps are plenty long enough. No useless molle attachment points. The climbing specific features, such as crampon straps, are easily removable. A clean, simple, but functional design. Tested on some of the most challenging climbs in the world. That one is my favorite, but there are other good designs out there.

For those few hikers that truly need to carry massive loads, there are other good civilian models to choose from. For example, see the Frontier Gear of Alaska Freighter Frame.
If you need to pack a massive load, this is the frame you want. They also make bags to go on that frame. Bullet proof construction. And it's even green colored!

While military gear is good for it's intended users, it isn't usually the best choice for civilian hikers. There are lots of good designs out there which are more appropriate for most users.