Far from useless against unprotected troops - especially in area denial and degrading enemy combat effectiveness. The real issue of practicality is that they’re a matter of mutual deterrent - if Side A starts using chemical weapons, Side B may decide to start as well. But as you mentioned, we’ve solved the issue of protective equipment pretty thoroughly, so in all but the most lopsided of conflicts (Iran-Iraq War, Syrian Civil War, police against protesters), escalation does not actually give either side an advantage beyond the initial shock, and introduces a lot of unnecessary defensive and offensive logistics, the total effect of which is likely difficult to determine. How many millions of dollars of chemical shells are worth keeping a platoon of soldiers in gas masks for a few hours longer? How many millions of dollars of chemical shells are worth the enemy shelling you in turn and forcing you to spend valuable resources and logistics lines on NBC gear? Who comes out with the advantage in this asymmetric exchange - the one with more resources, or the one with fewer? Nightmare to tell.

Russia currently is using chemical weapons effectively in Ukraine - namely, tear gas. Great for disabling dug-in enemies so mobik meat cube ingredients mass infantry assaults can advance. We (the West) also use chemical weapons effectively - we claim WP as a smokescreen, but its application tends to be very, uh, ‘dual-use’ in smoking troops out of entrenched positions. In both cases, the effectiveness relies on deniability and prevention of escalation.