But then I favour the big hole, two compression straps, one lid pocket, a flat back system and made out of Cordura of my old Alpiniste . It’s a 1994 vintage and in unable to wear it out.
Mine went back three times for repairs to stitching. I know what you mean though, a proper classic, simple alpine sack from before when alpine packs got lighter and more scrawny. I suspect the nearest modern equivalent would be a Macpac Sentinel or similar, but big bucks.
Once you get down below £100, back systems and foam densities tend to get quite basic, I think. Which is why I like Lowe Alpine, they seem to have stuff like that and the shape of lumbar pads etc, nailed.
Or Arc’teryx, again if you can find one at an affordable price – good luck with that, though SP occasionally has them. The outdoors industry’s dirty secret is that everyone seems to use Arc’teryx packs when they think no-one can see them. Sorry, that wasn’t much practical use.