Salami

OK, to be fair I think this is a decent topic to be talking about.
In the most simple sense, music written with the intention of expressing the sad feelings of the writer in a way that makes it obvious what their feelings are is what would usually be labelled "depressing", because it's attempting to share something with the listener, in this case an idea of what it's like to be them.

Just for the record, that's what I'd see as good songwriting. In one sense I don't mind what emotion the writer is trying to convey, I'm more interested in them doing it well.
I'd prefer to hear an insightfully written song that conveyed the feelings of sadness over a tacky, inane song about some poorly expressed sense of happiness.

Furthermore, I'd like to question the merit of complaining about something being "unjustly" labelled depressing. When you are unhappy, you want to hear someone who knows what it's like to be you, or who knows what you're going through. I see that as something of value, and would object to that being labelled as a bad thing.

Holerbot6000

Yes I agree - it's not necessarily good or bad, it's just part of the human condition. If you relate to a song like 'Ramblin' Man' by Hank Williams - there can, on one level, be a certain satisfaction in seeing yourself in that song - I'm a Ramblin' Man! Hank GETS me! - but on another level, it's a sad song because Hank is also saying, baby I love you but this is the way I am - and you can relate to that too. It might indeed leave you feeling a little depressed, but just finding that you have something to relate to, that you're not necessarily alone in how you feel can be a very enriching and valid experience, even if it's not always a happy one.

Salami

Well put mate!

I was wanting to say something on these lines but you've put it better.
Taking that slightly further, I was reflecting a bit along the following lines: the OP referred to music being depressing "apart from bringing up depressing memories".

I'd like to suggest that this isn't so simple - we can only feel sad through music because we already know what it's like to feel sadness and to be unhappy. Basically, I was listening to "How to Grow a Woman From the Ground" two nights ago, and the very fact that it was so sad and the imagery of the song so dark yet sung so beautifully , made me reflect on an intensely painful memory of the last month, the sequence of events playing out in slow motion. And the song made me sad because although it had no connection to the events it made me sad by association the emotions with the ones I felt.

So the point is that songs may have the effects of producing emotions in the listener which are depressing.