Do not even begin to assume what I have been through. The difference you might be failing to realise in your long essay on the behalf of others is that to go "through" something is to come out the other side.
You've already made your assumptions so I highly doubt you'll listen to me much further, not do I want to gain "e-points" by listing out all my ailments. I can assure you however, that I have received professional help for both depression and other mental conditions in my life.
The difference being, that my doctors and I were able to look at the root causes, and able to work out of it. Meds were weaned off as soon as I was put on them, and not looked at as a source of pharmacy income the rest of my life. Nor, now, a brainwashing device that can zap you for your hourly dose of Facebook ads. Thanks science.
By a large margin, the reason people get depressed is because their life is at odds with their expectations. The father is depressed because they want freedom. The teen is depressed because they want to feel genuine love, etc.
The only way out of that is to calm (which meds can temporarily help) then figure out a plan to make the life they do want, then actively working towards that, while managing expectations and inevitable disappointments. Sunlight and physical activity goes a long way in putting the body's regulation system back into action.
Everyone just gets stuck up on "ok, meds." And don't follow through with the rest of it - actually improve your life - and expects everything to be better somehow. Painkillers while keeping the hand on the stove.
Tldr get fuxked