You're not wrong, but it's worth noting that there are some really obvious things we could do which would cure a lot of people. Not, for example, requiring people to work 40 hour weeks when there isn't enough work to employ the entire populace 40 hours a week is one obvious measure, because it removes the need for people to sit at their desks doing literally nothing, and would result in more people being employed. Restructuring business so that people are rewarded for providing value instead of acting as gatekeepers of value would be another. Removing the near-constant bombardment of advertising from our emotional and social landscape would remove a lot of demands on people's attention and allow them to focus on activities they find meaningful.

The fact is, people are depressed because the powerful in our society benefit from treating the majority of our society like shit.