Hey there. How bad would you say your anxiety is when you are around civilisation? If it is pretty bad, I suspect your therapist's idea was to slowly increase your exposure to the stressful environment, until you become accustomed to it. If five minutes at the grocery store is mundane, that could be a good thing! This type of exposure therapy is also used for OCD treatment, because, scientifically speaking, most people when exposed over time to their triggers, become desensitized to them (I'm sure you're already aware of that part).

Anyhow, I dealt with mild agoraphobia some years ago, for a short time, so I don't feel fully qualified to comment on this. But I have seen some success with exposure treatment. I hope someone who has dealt more directly with agoraphobia will chime in here.

Hoping you get to the bottom of this.