I say this as someone who rather successfully turned things around with a therapist - I simply did not have it in me to have those conversations with others and I didn't feel I had the relationships or support to do so (in retrospect I probably did, but that's the thing about mental health).
I don't think your diagnosis is wrong, particularly - there's a lot in the modern world that promotes alienation, feelings of low self esteem, and depression, but I think a lot of people find themselves at the bottom of the well before realizing quite what's happening and without the support structures to get out on their own.
(Edit just to note that, like physical health, mental health is not just the consequences of one's own actions - both genetic predispositions and unexpected life events can necessitate professional intervention by no fault of one's own. It's not what we're talking about, but just so nobody takes my post to be a psalm from the church of the self-sufficient.)