I'd encourage you to read the article. Chemical weapons are effectively useless against a well-trained "modern system" army. Part of that is the chemical warfare equipment and vehicles, but mostly it's cover-and-concealment. If you can actually find the enemy, it's much faster and simpler to use the other vastly destructive munitions that modern militaries have.
I did, and it’s really not very convincing at all. It uses an example where a terror group in Japan was able to injure thousands of people with a chemical attack, and act as if this is… not a particularly effective outcome?
Additionally, that “if you can find them” is doing some pretty heavy lifting. The range of explosives and kinetics is hilariously low, and the actual percentage of your military with the level of mobility he seems to be referring to is infinitesimal.
This argument more correctly explains why chemical weapons aren’t a great defense against precision strike groups. It also doesn’t get into detail with concepts like dropping a bomb right in the middle of a firefight knowing it literally cannot harm your own troops, short of the physical metal accidentally falling on one of your own troops.