Keeping your head down as low as possible on a rifle (with low sights with a low-slung butt stock) was probably a priority during World War I : static warfare over blasted-open flat terrain where riflemen often engaged in sniper duels from trenches and shell holes at long distances or had to dodge getting raked by emplaced, dialed in heavy machine gun fire in No Man’s Land.
Low slung butt stocks are fine on bolt action rifles where you have to pause between shots to manually cycle rounds, but in semi and full auto they cause pronounced muzzle flip and inaccurate automatic fire. As warfare evolved into mobile blitzkrieg warfare during WWII, soldiers had to maneuver and keep their heads up and on a swivel for closer range combat with full and semi auto fire. The Germans developed the StG 43 / 44 with taller sights and a straight line butt stock, along with a medium caliber rifle round with selective fire out of extended mags to press their technological and tactical advantages in combat.
First, I agree that stocks being inline w/ the bore are tremendous mechanical advantage with rapid semi-auto or f/a fire. Muzzle devices like brakes, comps, and hybrid brakes & comps also can serve to accomplish the same. Double or triple them up for max advantage... Also remember the difference between full caliber/power cartridges and the intermediate and small caliber cartridges/caliber that now are general issue infantry weaponry...
Second, I don't think optics
have to be cowitnessed with irons in this day and age given improved reliability of optics. But there can be an advantage in cowitnessing depending on optic/reticle/magnification/etc. If not cowitnessed, there is also a benefit to having irons and an additional benefit to having your optic on a QD mount.
Third, I think it's worth noting that the Vz58s' build quality and performance appears to indicate a nation that was looking to increase capability and therefor survivability of its soldiers, primarily based upon lessons learned in WW2.
Fourth, your comment's historical take is a pretty big oversimplification...
Like assaulting WW1 trenches, human wave attacks have also occurred in WW2 (look at pretty much all Russian advances pushing Germans out of Russia all the way back to Berlin), Korea, Vietnam, various African conflicts, and up into Afghanistan.
Temporary and hasty firing positions remain a staple of the US infantry -- effectively a modern trench system whenever possible for cover, not concealment.
Sniper and counter-sniper battles have occurred in every major conflict -- Juba Sniper of Baghdad for instance in Bush 2 Iraq War. Sniping in Afghanistan regardless of inherent accuracy has been well document. Modern fighting positions referenced on previous and their shooting only or primarily to oblique are also to help mitigate the efficacy of snipers...
Machine guns in WW1 like most since but also in bolt action rifle preceding were as much about beaten zones at distance as transversing sectors. Look to the British's volley fire with Martini Henry and Mad Minute with Lee Enfields, both predating WW1. WW2, it was the Germans' light and medium machine guns that were widely fielded throughout the war, not the Sturmgewehr, that defined the biggest advancement in German small arm combat and tactics.
While the US hasn't fought a peer or near-peer military since WW2, the US air, sea, artillery, comms, information, tech, etc, dominance in modern conflicts has allowed us to transition to largely a vehicle-borne infantry that has been engaging irregular enemies in 4th gen warfare where there's no clear front lines and no clear enemy and civilian, but such dominance and confusion is far from certain in possible future ones. In such cases, hard-learned old and forgotten lessons of 3rd gen warfare -- what you're referencing as no longer applicable -- will have to be relearned...
