The writer dismisses .308/7.62mm NATO out of hand for long range shooting - so how far does he see the conceptual ranges to be?
The flipside is the usual pile-on that the 30 caliber is 'too much gun in town' & 'only suitable for long range shooting in open country' is either ignoring or ignorant of the practical tactical roles. Such as being the minimum caliber (308-311) for use in immobilizing non-hardened up vehicles with. Also prime for decisively immobilizing occupants in the passenger compartment of said vehicles if need be. The 223s don't really cut the mustard at that, well unless there's an M249 handy you could hose it down with. The other is turning moderate forms of cover that other small arms calibers can't efficiently defeat (if at all) into mere concealment - the 7.62 NATO will perform well at that. Anyone who anticipates such threat scenarios being a possibility in their given area/situation should upgrade their arsenal.
Early in my Marine Corps career, we referred to the M-16 as "Matty Mattel" and the "Paint Chipper" and the 5.56 improved somewhat a bit later but it's still .22LR with a better press agent.
While I was working for the Marine Corps Warfighting Lab, a friend of mine commanded a provisional MP battalion in el Anbar, Iraq and he asked me to locate and send M-14s because the M-16s weren't cutting the mustard at the distances and with the kinds of structures they were dealing with over there. I found 2,500 Condition Code "A" M-14s in storage at Albany GA, then found the magazines, gauges, TMs, and the M80 Ball ammo to send them - and I was decisively stopped in this project by some pompous Major at HQMC (as all good ideas are). My buddy had to stick with the paint chippers.
The biggest roadblock to progress and combat effectiveness are staff officers hanging around the Pentagon and away from the gunfights.