Thanks for keeping on topic, heh.
You're right in your assessment of the weaknesses of infantry. However, do you think there are ways for the infantry army to nullify those advantages? For example, teams of manpad operators for taking down helicopters, teams of anti-tank squads moving through mountains and taking down tanks and APCs.
Again, it depends on the operational (division/corps/group army level) and strategic (military theater/political-level) goals of the war. Put bluntly, the light infantry force will have difficulty mounting offensive operations, but can hold its own defensively, provided there are enough trained troopers and no morale or supply issues.
Is the light infantry force trying
defend a particular terrain feature (e.g. a river, a mountain range) on an operational level? Then yes, those tactics work--but only if the combined-arms corps or division commander lets infantry running around at 15 km/h catch up to his tanks and APCs driving around at 50 km/h or runs his helicopters through terrain without clearing it with cluster bombs and napalm beforehand.
The same applies on the strategic level. If the light infantry force is resisting an occupation of a country--then yes, it can make the combined-arms forces bleed a lot, as Vietnam, Afghanistan vs USSR, and Iraq 2.0 have shown us.
But in offensive operations, light infantry simply can't do it. A whole bunch of men assembling bereft of mechanized transport will be horrifically vulnerable to most modern "see-deep/strike-deep" weapons.
(The obvious exception to the rule is the Chinese PVA in 1950-51 Korea. In that case, the US lacked the deep recon platforms that, for example, can detect massed amounts of infantry in real time--such as spy satellites with infrared capability--and hence the US couldn't place accurate fire support down on them.)
A better example of light infantry getting crushed would be the Iran-Iraq War of the 1980s. In that case, Iraq had a smaller, Soviet-style (loads of tanks and artillery) combined-arms army versus the Iranians, who were under US sanctions at the time. The Iraqis had a rough go of things until they changed their doctrine (from offensive actions to elastic defense with powerful armored reserves) and got US spy satellite feeds on Iranian troop assembly areas. Then they could just wait until the Iranians massed up their light infantry and shell the place with nerve gas and incendiaries, and if the Iranians broke through, then the light infantry would be cut off by a rapidly reforming Iraqi front line and then engaged in one-sided massacres by tanks, helicopters, and lots and lots of artillery. Cue 3-1 and 4-1 casualty ratios for the last three years of the war in favor of the Iraqis, while the Iranians gained essentially no ground.
From a technological standpoint, the dynamic has shifted more and more in favor of the combined-arms force.
From a fire support perspective, see-deep/strike-deep platforms can now react in real-time across "wideband" command and control channels. What this means is that an artillery battalion attached to Brigade A can see what is happening to Brigade C in real-time (either from drones or satellites), and with can support Brigade C whatever is needed (anti-armor, anti-personnel, smokescreens, high explosives, napalm) with only a cursory nod from the division or corps commander. And, thanks to advances in C4I, they can do this across an entire front line that is up to 1000km wide and 100km deep. Meanwhile, the light infantry force can't coordinate nearly to that degree--they'd be lucky if they could call on fire support from mortars 10km away. What this means is that the light infantry force is now always in range of real-time, coordinated, firepower from the
entire opposing army, whereas the combined-arms army only has to worry about the enemy directly around them.
From a comms and coordination perspective, combined-arms armies also have the advantage of mobile C4I nets and electronic jamming, which means the corps or army-level commander can pass orders around to every unit, while the light infantry force, with completely jammed long-range nets, essentially fights like a whole bunch of disjointed infantry battalions. An infantry battalion commander with no clue what is going on in his neighboring sectors is a commander that is probably going to die soon with the rest of his troops.
Finally, from a supply perspective, the light infantry force will have serious replenishment problems within one or two weeks of fighting. People can only carry so much food, water, and ammunition on their shoulders, and how is a light infantry force going to coordinate well enough to get the right ammo and supplies from rear area warehouses without trucks and proper logistics units? On the other hand, most modern militaries (NATO, Russia, China) have finally gotten the hang of how to properly resupply a combined-arms division or corps from two weeks to forever without any hassle, even if that division or corps is halfway around the world.