Hair loss is definitely related to poor hormonal balance and finasteride is probably the worst way imaginable to treat it. It’s more like torture than treatment, and you’re just lucky you didn’t end up permanently impotent like some men do.
The very fact that finasteride works demonstrates how influencing your hormones can affect your hair. I don’t see how a doctor can at once prescribe it and claim there’s nothing wrong with you. It’s all well and good blaming everything on stress until you consider that susceptibility to stress is yet another symptom of disrupted hormonal balance, much like susceptibility to infection.
You’re experiencing many other obvious hormone problems that are clear from changes in libido, sexual performance, prostate (possibly enlarged?), fatigue, depression (SSRIs bring as much hormonal doom as finasteride) etc. As long as you’re experiencing these symptoms there’s value in continuing to investigate.
I’d imagine your doctors would’ve never checked things like oestrogen, progesterone, T3 and reverse T3, prolactin etc. If you’re optimal for all these then you can believe in the “genes cause hair loss” theory in the face of everything epigenetics has shown us over the past couple of decades.
Danny Roddy’s ideas on hair loss are interesting. You may not find all you need to know or agree with him on everything, but you might have what you believe about hair loss, serotonin and a few other things turned upside down. As long as you can’t get out of bed, have trouble digesting food and your orgasms suck, you should expect to keep losing hair. Take this as motivation to investigate though. If you didn’t have these signs of hormonal disarray, you’d be stuck believing in evil old uncle 5-alpha reductase.