What do you mean “if they were really effective”? We still hand out CBRN gear and train in how to put necessary parts on in seconds, because that’s often how little time you get before you’re permanently incapacitated. Mustard gas alone should prove this, and that’s an OLD chemical weapon.
Nowadays we have riot control agents that can be tailored to demographics, react more violently in the presence of sweat, or contain psychoactive ingredients. Nanoparticle dispersion bypasses common gas masks and clothing protection. Even if you’re completely geared up, they can be engineered to last on surfaces for a long time, or react only in the presence of certain triggers. Imagine thinking you’re safe until someone turns on a certain light bulb and you cook inside your protective gear because you were actually exposed 12 hours earlier in an undetectable manner.
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.