My apologies if our rather combative exchanges in any way exacerbated this.
But I will say this. While it's fairly evident that depression has a genetic component, an environmental component, and can occur after trauma, you do need to approach it as an episode of "what can I do to make my life better" - some of which may be a change in environment. But moreover you have to think long and hard about why you are in the rut you are in now, and what you can personally do to make it better.
I know you're not going to fully agree with this, but entertain me for a second. I would say that the ideologies you have attached yourself to is not good for you at all, and may make your depression worse. Obviously you became attracted to it by what you were feeling yourself, but I think you have made your own state of mind worse by accepting its conclusions. If you think of everything as systemic, everything is already set in motion and you are just a small mouse within it - why do anything to change yourself if it's all structural? This kind of determinism is akin to being fatalistic. Here's the definition of wikipedia:
"Fatalism generally refers to any of the following ideas:
1.The view that we are powerless to do anything other than what we actually do. Included in this is that man has no power to influence the future, or indeed, his own actions. This belief is very similar to predeterminism.
2. An attitude of resignation in the face of some future event or events which are thought to be inevitable. Friedrich Nietzsche named this idea with "Turkish fatalism" in his book The Wanderer and His Shadow.
3. That acceptance is appropriate, rather than resistance against inevitability. This belief is very similar to defeatism."
Either way, the best way forward for your own mindset would be to think about what can you do to make a positive impact. How can you be productive? What makes you happy? What is a realistic way forward, step-by-step? Hang out with friends (positive ones, not one who bring you down).
Moreover I think some of the messages you're listening to from your broad "Social Justice" ideologies are themselves coming from people with mental illnesses, whether that be people who are depressed, bipolar, or who have some kind of personality disorder like Narcissism PD or Borderline PD. Even if they're not, they are almost certain to contain very negativistic, very bleak, very dire views of the world. You really need to focus on more positive messages, or at the very least realistic ones. I'd slowly divest yourself from whatever sources of information that have these tendencies, and move to ones that tend to make you happier and more enlightened. I had to do that myself as I started to figure out that the progressive messages on places like dailykos were unbearably negativistic and whiny, as well as even entertaining the doomsday rhetoric from the exact opposite side of the spectrum - Austrian hyper-individualists (thanks, brother & sister-in-law!).
Anyways, take care, get lots of sleep, start execising and building muscle, and start hitting on women (in person or online). That should also make you feel much, much better - make you more attractive and more confident. Good luck, you can pull through.