its their main defining character trait.

And what's worse is that most of these games don't really inspire hope or idealism.

It truly a constant state of wallowing and retreading. The very thing that depression makes you do; self-deflecting than self-reflecting, thus leading to a lack of self-growth, the strongest form of treatment against depression.

Its the reason why a lot of these characters tend to be static, because why do THEY need to change? The world/other-person is the one that needs to change, its the one that made me like this afterall.

A good example of character growth who has depression is ironically not from an indie game: Psychonauts 2 Bob's bottles. In the mind of a character's sorrow is a kind soul that has been marred by tragedy and self-hatred. Its only when he realizes that his depression is clouding the truth is when he start's to show his true self.