It's not that chemical weapons have no military use at all, but if you make soldiers immune then the only people killed in gas attacks will be civilians, and that's not so far off from the world as it is.
Frankly, I'm surprised they're not used more often. I think we'll see a massive scale chemical attack this century. There's a lot of political instability fomenting across the planet.
It honestly amazes me that the “people” in charge of some of those countries had such restraint
The situation was a bit different in WWI when only Germany really had the capability to make extensive use of them.
Germans had already had that experience https://en.wikipedia.org/wiki/Attack_of_the_Dead_Men
"The gas, "caused the grass to turn black and leaves to turn yellow, and the dead birds, frogs and other animals and insects were lying everywhere. Terrain looked like Hell."[1] The Russians either had no gas masks, or had poorly made ones, and most soldiers used their undershirts as masks, with many soaking them in water or urine.[2] Sub-Lieutenant Vladimir Kotlinsky, the highest ranking Russian soldier to survive the initial attack, rallied the other surviving soldiers, and they elected to charge the advancing German lines.[2]
Over twelve battalions of the 11th Landwehr Division, making up more than 7000 men, advanced after the bombardment expecting little resistance. They were met at the first defense line by a counter-charge made up of the surviving soldiers of the 13th Company of the 226th Infantry Regiment. The Germans became panicked by the appearance of the Russians, who were coughing up blood and bits of their own lungs, as the hydrochloric acid formed by the mix of the chlorine gas and the moisture in their lungs had begun to dissolve their flesh. The Germans retreated, running so fast they ran into their own traps.[2]"
>had such restraint
it isn't restraint. On a real battlefield, especially a modern one with all the tanks, APCs, etc. having NBC protection, chemical weapons have very low resulting efficiency coming at very high price. It is a very unreliable opportunity weapon with a complex logistics. It is much more useful as a threat than as an actual weapon.
Instead of soldiers, i think the work in the original article will in the coming future be used to "fortify" people working in harsh/toxic/dangerous conditions.
With a serious immediate threat, you can force the enemy to wear the full NBC gear. That impedes everything. They can't effectively eat or wash, their vision is restricted, and they might get heatstroke.