A character flaw is a relatively painless way for the audience to confront their own flaws / fears of weakness.

Having a dead wife, strictly speaking, isn't a flaw. Grieving too much or too little over the death of a spouse is.

I bring this up because a viewer who has lost a spouse may identify with a character who has lost a spouse, but there's nothing necessarily deep about that bond. Someone who hasn't experienced the death of a spouse won't feel the same way but will probably feel some sort of sympathy for the widow / widower. Still not very deep.

But if a character's experience of grief is flawed in some way (too much or too little for example), then the audience can identify with the character on a deeper level, whether they've lost a spouse or not, whether they have a flaw about grief or not, because the audience is aware of the flawed nature of their own experience. And so the audience is able to confront their own imperfections, even if only vicariously.

It's not even important that the protagonist (or other character) overcome the flaw (achieve wholeness / integration). The character may be tragic, but the audience is still able to identify with the character's flawed nature and confront their own flaws (perhaps even more than if the story slaps on an artificial happy ending / arc).