I think you're overstating the success of chemical treatment. I'm not extremely well versed in the subject, but I've read a number of books and articles that seriously call into question that idea.
It would seem that "talking about it" is actually more effective than medication in many circumstances (e.g. the research on cognitive behavioral therapy versus medication).
The consensus at this point seems to be that we do not have any real causal theory for most mental illnesses, including depression.
You might have an Aristotelian sense of "success" in mind here (meaning that it covers something like the long-term overarching benefit of the person), but I don't. I just mean success as in, anxiety medication actually improves anxiety; depression medication actually improves depression; attention deficit medication actually improves attention. Whether there are better ways for us to achieve long-term outcomes is a different issue.
Except sadly that's not true. Anxiety medication usually does not improve anxiety. Same with the rest. But sometimes they do, and when it works it's enormously valuable to people.
Medication and talk therapies (including CBT) are more or less tied, from what I've heard.
Antidepressants are not much more effective than placebo, which is a problem if you're a drug researcher, but as a patient it doesn't really matter that your relief actually comes from placebo effect.
It would seem that "talking about it" is actually more effective than medication in many circumstances (e.g. the research on cognitive behavioral therapy versus medication).
The consensus at this point seems to be that we do not have any real causal theory for most mental illnesses, including depression.