Actually, bipolar disorder is not seldom treated with antidepressants, but almost invariably together with a mood stabilizer, not in monotherapy. In monotherapy antidepressants had near distasterous effects on me, but in combination with a mood stabilizier they worked just fine for many years. I don't know what my serotonin and dopamine levels were, but I do know that I didn't have any episodes during these years.
As you say, paraphrased, there are enormous individual variations. Antidepressants can have no, little, or adverse effects, sometimes very serious, on some people. However, that majority of all studies I've found show that antidepressants work for the majority to one degree or another. Warnings about potential risks are fine, but categorical dismissals aren't, in my opinion.