I believe that the "root causes" of depression are what actually deserve any attention, and they are a combination of genes, society, environment and psychology that has been ingrained by these factors. Depression is like smoke from a fire, and we're currently treating it by installing fans to blow the smoke away.
This has been supported by research psychology about what makes a fulfilling life: a sense of autonomy, mastery, and relatedness. I guarantee you that someone missing even one of these will be "depressed." What do we say then? We don't think about how the environment he's living in is not encouraging these things, and we don't think about specific actions he can take to improve these factors.
No, we just say "Depression!" and tell him to go the therapist. Most people in modern society have eaten this psychiatry bullshit whole and as a consequence are more fit to tend houseplants than to maintain even the shallowest of friends.
So NO, what made the people who went through living hell different wasn't the fucking fake concept that is "depression", it was the SUPPORT.
I say we don't ever talk about depression. The very existence of the word "depression" pushes real societal and individual shortcomings and responsibility off the table.
We talk about what's going right and what's going wrong in the person's life, and if we don't have good advice on how to fix the things that are wrong, at least stop trying to grandstand and signal your social status with some useless platitudes and endlessly repeated refrains about the benefits of therapy and medication.