It seems to me the best way to fight depression, is to contimually distract yourself (particularly with an activity you can control), from whatever is depressing you. As if, by being busy, so much, that you end up forgetting about those depressing things. I know it's easier said than done, but to me, it seems to work if you're able, whereas focusing or dwelling on the depressing things, seems to further depression.
But other people who suffer from serious depression do so in ways that can be connected to their life circumstances and the framework of meaning they build for themselves around it.
I think one of the biggest disservices we do to people suffering from depression is lumping those two categories together.
It's like we have a single diagnosis for "bleeding" and very rarely distinguish stab wounds from hemophilia.
The theory you're describing is "depressive realism". It's hotly contested. In some ways, depressed people can make more accurate assessments, as most people have an optimism bias, but their assessments get unrealistically over-pessimistic as time passes.
Given the general tech-dystopian living conditions and % distribution of non-free software throughout the population: depression would be near universal if this was truly the case.
I suspect those downvotes are due to people recognizing that it implies depression is sometimes within the control of someone afflicted by it and conflating that with blaming the person afflicted by it. People seem offended by critiques of modern ideas that rationalize away an individual's control, agency, and especially culpability for their behavior or outcomes. Sometimes these rationalizations are fair, other times not.
People who are sick either continue to be sick, get well, or die. No matter what diagnosis or treatment you give to someone, they either get better, don't get better, or are removed from the conversation. We never hear from the dead again, the people who get better insist that you saved their lives, and the people who don't get better will be attacked by the people who did for not believing or trusting you enough.
But I think mental illnesses challenge our very old notions of free will, willpower and control. How much are you really in control when the mental structure for motivation in the brain is broken? Personally, it's not like I pulled myself out of depression. I just took advantage of a "break" my brain gave me.
So trying to figure out whether depression is reasonable is usually a trap, and will not improve the person's life. The thing to do is to manage the feelings, treat the depression, and revisit those topics once the depression lifts.