Not the GP, but I'll comment about ADHD, since that is what I have relevantly read research about.

For ADHD, it appears that therapy < medication < therapy + medication.

When compared head-to-head, therapy is almost as useful as medication, but the issue with therapy is that once the patient stops attending, the benefits tend to diminish rapidly.

However, therapy tends to have less side-effects and less stigma. According to some research, medication efficacy also tends to diminish overtime as well.

For other conditions, I cannot tell you. I feel like it would be too large of a brush to try and paint with. I could see conditions like personality disorders not benefiting from medication as much as therapy. Conditions like schizophrenia might not truly benefit from either. For conditions like depression and anxiety, I think the medications are efficacious if not perhaps less so than therapy, but do not quote me on this one.