Most of the "treatment" is apparently just telling people to stop feeling sad [0], or giving them drugs
[0] https://old.reddit.com/r/thanksimcured
but no one bothers to take the time out to sit down and figure out WHY they feel sad and FIX THAT FOR THEM. That takes too much work.
Sometimes depression is this vague feeling that this world is just wrong. That Damocles' sword of mortality. The nagging sense of ultimate pointlessness. You can't really "fix" that. But having stuff to ignore it helps, like video games :')