with 1 caveat. A surface must be as easy (or easier) to remove than it is to apply. .
I hadn't thought of this but I think you're right. Like there was a room full of poison which I wanted to get past. I did what I'd do in Divinity, which is blast it with fire to get rid of it, but that had no effect. I assume they got rid of reactions like that because it would be too extreme for the more subtle nature of these rules, but in a way by being half way in between it actually makes it less manageable.
I think I know the area you're talking about, and shooting a firebolt at the ground in that area should cause it to explode into flames like it does in DOS2, the problem then is you have to put out the fire and run through it before it starts emitting the poison gas again. This worked fine in DOS2 cause I honestly just tanked my way right through the fire surfaces, but in BG3 since armor doesn't work the same, it makes this small obstacle into a massive one. Mainly because the only way I had to put out fires at the time was 2 bottles of water and Shadowheart's Create Water spell, which ate up her spell slots and wasn't even enough to actually get me through all of the poison clouds. I find that at the very last poison cloud, there is in area where you can jump right past it off on the left side, so that helped a bit.
