I believe in the idea, but understand the necessity of limiting it to permanent and/or degenerative conditions. Mood disorders, personality disorders and addiction don't count. If someone in mental anguish wants to kill themselves badly enough they will find a way, even if you're afraid of pain or failed attempts it's not difficult to score a lethal dose of heroin or fentanyl in a shitty neighborhood. If someone wants to die but is too physically feeble to do it themselves and there's no hope of that changing, that's when euthanasia should come in. The hard questions are the ones where the person acquires a disability that is permanent but won't necessarily get any worse - I'll use my personal example: I would want to off myself, no question, if I ended up blind. Sure, plenty of blind people lead perfectly happy and productive lives, but I just couldn't fucking do it. Not worth it to me. I don't feel the same way about ending up, say, paraplegic, but maybe some people do - Should it be an option for them? Who is to say what conditions should or should not qualify? The criteria here (Canada) is that the suffering/decline/disability is both permanent and intolerable to the person, but if they think you might acclimate to the condition I don't know if they try to talk you out of it or just deny your case and make you reapply later. As far as I know anyone with a garden variety mental illness who applies is promptly told to fuck off. I'm not sure about dementia or Alzheimers because by the time those get bad the person usually isn't in any shape to make an appeal.
I don't think it would lessen the need for hospice care or supportive care all that much, it certainly doesn't here. But with so many people in the US facing their family's financial ruin if they get very sick, I think that could influence a lot of peoples' decisions. That is where I think it might be vulnerable to coercion and abuse. It's been legal here for a while but is still really rare because massive unmanageable hospital bills aren't really a thing, and the reality is plenty of old, sick or disabled folks need help with all their daily personal tasks but are happy enough watching TV all day doped up on morphine.