I think people shy away from open discussions of these issues simply because it’s unpleasant, a downer, etc and frum yidden are usually upbeat and positive. I’m not saying that it’s the right way, just I think that’s the cause of it, not arrogance or a desire to portray an unrealistic perfection.
There’s also a stigma in the world in general regarding mental health issues, because try as we may to frame it as no different than physical health, there is a difference and people’s wariness is understandable, albeit harmful to those who are suffering and who want to feel normal and comfortable with who they are