Now that I write that out I guess it's like every other health disorder. We're pretty good at a subset of them, so-so at another set, and have no flipping clue what to do about the last set.
I'm broadly generalizing here, but depression caused by a physical condition (e.g. an autoimmune deficiency) can typically be cured by attacking the underlying cause, but depression caused by a psychiatric condition is much harder to "cure" in the traditional sense and instead can be managed via modern pharmaceuticals. Now, those drugs come with some strings attached, but if they help a patient get out of the bed and function in the morning (as they do with my wife) then that's a net positive, but we're realistic about the fact this is likely a life-long battle that will require constant work to stay on top of.