> If you have an objectively crappy life, but not just ignore it and instead are incapable of even noticing

Noticing it is very different from being depressed about it.

> What does "normal" even mean in this context? Are we talking about something measurable?

Let's take a trivial example. Person A is depressed because he is unhappy that he doesn't make enough money to travel and buy nice cars. Now take all the people who are unhappy that they cannot afford to travel and buy nice cars. Most will not be depressed - they will merely be unhappy about it.

Person A isn't depressed because he can't travel and buy nice cars. He's depressed and he can't travel and buy nice cars. He's mistakenly coupling the two.

Another tell for these kinds of things: Ever know someone chronically depressed who blames it on X? Then somehow, X is resolved. There may be a temporary improvement, and they go back to being depressed again, only they now blame it on Y? Somehow Y gets resolved and some months later they're blaming it on Z.

Everyone has problems. Including those who are not depressed. Fixing X, Y, Z, AA, AB, and whatever else is not going to take care of the depression.

On the flip side, people who do not suffer from depression make the same mistake: They claim they are not depressed because they "choose" not to let the problems get to them. Self serving beliefs!