I do not disagree with that.
> if you have the right mix of brain chemistry and genetics, you might be screwed.
Right. I experience no euphoria whatsoever from any opiates (in any dose)[1]. Blessing or a curse? I personally call it a blessing because I have an addictive personality so I would get hooked up on it too. It works for my pain and my depression & anxiety, and for that I am grateful, all while not causing euphoria, all it seems to do is just mood stabilization, i.e. I am less likely to be emotionally volatile.
The constipation side-effect can really be frustrating though, but thankfully I can manage it through diet and skipping doses.
[1] It possibly has to do with my neuro{biology,chemistry} and my brain lesions but who knows. Psychiatric medications never affected me the way they typically affect others and I have gone through _a lot_. It might be genetic, metabolic (as well), I have no clue.
I had an opiate after surgery once and the constipation was so bad, it was worse than the pain it was supposed to be treating. I switched to Aleve instead, which was both better at pain management and had fewer side effects.