I feel like this story was trying to teach too many lessons at the detriment of the story. The ending wasn't really believable to me, with Dorcas planning to flood the world/country's water supply with an endless supply of drugs. (Or at least endless until everyone was dead from neglecting their bodily needs.) That just wouldn't work and I don't understand her motivation for it either. Getting pleasure-juice for herself is one thing, but providing it to/inflicting it on everyone? Given the strength of her lust for the juice, I don't think Dorcas would be able to abstain from using it for months once she had it in order to develop her master plan.
I did like the twist of biology that made the main character immune to the alien drugs and unable to empathize with the addiction. I also enjoyed that the first step towards rebuilding society didn't need to be huge or groundbreaking. Just getting some people together to see a crummy band was enough.