How are they catastrophic? Not being antagonistic or anything but I just thought it was ED until you realise you have ED, then stop taking it, and the effects wear off.
Maybe I'm being naive, I probably have "alpha genes" (not bragging, as we don't have any choice on our genes) and my libido initially was actually stronger for a while. I've never had any issues with ED, even drunk or on drugs, but within a week of taking finasteride I would get a horny thought and it's ready to go, or a girls knee could brush my thigh in bed and literally within a handful of seconds I'd have a full erection.
So obviously I don't understand sides the same way most people do, my view is skewed and when I came to that realisation some months ago I started to feel that it's irresponsible of me to constantly tell people to jump on treatments when I (or anyone else really) doesn't understand the stats of how it affects people, and now your post is telling me not the stats, but how it severely affects people, and this I never understood before.
So yeah, what happens exactly?
In my humble opinion, permanent erectile dysfunction is a catastrophic outcome.
There's now a modest amount of research on post-finasteride syndrome in addition to the thousands of anecdotes, which is all there was a few years ago. Finasteride inhibits 5AR in each of the skin (good), blood (not so good) and cerebrospinal fluid (terrible). It seems that in the third case, even if you stop taking finasteride, the 5AR might not recover. A huge number of people report side effects that last years after stopping the drugs (so effectively permanent) such as brain fog, depression, erectile dysfunction, slurred speech, impaired sleep, et cetera.
I read a few of the anecdotes and it was depressing so I stopped. There are mediocre solutions out there that sometimes work, such as going on 21-day water-only fasts, testosterone replacement therapy, et cetera.
I was on finasteride for ~1 month at 1.25 mg/day, so I've taken ~38 mg of finasteride in my life. I hope that I did not permanently destroy the allopregnanolone in my cerebrospinal fluid. I was getting slurred speech, reduced ejaculate, and reduced sleep while on finasteride but now that's over. But the side effects might creep on me later.
I'll consider finasteride if I'm diagnosed with prostate cancer. My father got prostate cancer in his 70s, and died in 2012 a few months shy of 78.
ETA: Your alpha-maleness refers only to the effects of finasteride due to the bloodstream changes: less DHT, more T, more E. It has no relevance on what happens to your cerebrospinal fluid.