No one has used Chemical warfare in the West since 1918 for a similar reason.
However, that doesn’t mean it is off the table. I only takes one nation to break the ice.
One bomb could have ended Vietnam and Korean wars. They weren’t used. The political will just won’t be there, ever.
If the history of warfare teaches anything at all, it’s that when a nation becomes truly desperate it’ll resort to anything.
The whole chemical warfare comparison is a red herring. Chemical weapons are counterproductive, and have, in any case, been used in the Middle East quite recently.
Nevertheless, I hope you’re right - I do hope nuclear weapons are never again employed.
I just don’t have your faith in the sanity of the human race.