Depression and for that matter any mental health condition is as individual as the people who live with it.
Making assumptions that people can't do those things or that they can does them a disservice and is disrespectful. In reality many may be able to do these things or others, to varying degrees on some days, if they can't on others, perhaps with support or adjustment. Many have good and bad days but what this means is individual too. Just because someone can work or go shopping it doesn't mean their condition isn't serious or real, just they can do that at that moment. Similarly someone who can't isn't giving up, not capable, or not trying, they just can't do it now.
It isn't helpful to say cheer up, take exercise or change your diet, for example, its a serious health condition and feeling better may take a long time. Better may also not mean not having any symptoms, or never havig it again. Better is relative and different for everyone. Each person knows their situation and needs best.
Talking about mental health ends stigma and helps others do the same.
