Saying that simple phrase is not a critique of his mental state. He just wasn't playing football the way he had in the past. I said this about him several times. Not once did I ever think it was about depression. I've had my own person battles with mental illness. Wouldn't shame anyone for theirs.
YET, there were good reasons to be critical of Mangum. If you are the QB at BYU, you are going to be scrutinized. I would guess the majority of people saying anything are not trying to bring his mental health struggles into it.