When I was a starving college student, milsurp gear got me into the outdooors, but over time I replaced it with far, far better civilian gear. Military gear today is much better than in my youth, but so is the civilian gear.

Fit is all important with a backpack, and most high end civilian packs have some pretty sophisticated adjustments, coming with a surprisingly thick manual. Get thee hence to a good outdoor store (REI or better), rent some good stuff, and take it out on some long trips, not just overnight, before you make the major purchase. You can also borrow from friends.

Most people don't devote the time and effort to this, and most people walk around with ill fitting backpacks.

The kindest thing I can say about your Alice rig is that it is obsolete. It belongs in a museum, not on your back.

BTW, I followed this route some years ago, renting a large Mountainsmith rig from A16 in Los Angeles, taking it out for an intensive weekend trip. Twenty years later, that pack has seen intensive, hard use, and is still in service. Mountainsmith is just one of several quality brands; it is the fit of the pack to your individual bod that counts, not the brand name.