I agree, that part of the discussion is defining "cure".
The "surgery" analogy: diseased organ is surgically removed, healthy, compatible replacement organ is installed (grown from the patient's own cells) recovery period with rehab therapy = lifelong cure.
The "diabetes" analogy: disease condition requires frequent, lifelong monitoring and self-treatment by the patient. But that really isn't a "cure", its just "maintenance". Insulin therapy does not stop the diabetic process, it just manages it.
So, you are right and the success of any therapy (even current therapies) that require long-term cooperation and participation of a responsible patient is going to have only limited success.
But a "surgical" procedure or a one-time Pill that cures all, or a preventative Vaccine? That would have the most success (based on availability/price) and would truly be like a miracle.
What would a world without con-artists, rapists, murderers, and sadistic monsters be like? What if everyone had both cognitive and affective empathy? What if everyone were born with a complete, fully-functioning brain and normal intelligence? What if there were no more terrifying psychosis, no more suicide-inducing depression, no more crippling anxiety?
Would we all become bland and boring, or would we be freely and happily exploring new horizons in science, the arts, and education? Would it unleash human potential for creativity and positive evolution, or would everyone having perfect mental health turn us into a kind of ant colony?
(Are some ants born psychotic, intellectually challenged, or sadistic? Do some ants become brain-damaged and therefor a danger to the colony? If there are crazy ants, what happens to them? Have ants failed to evolve higher intelligence because they're all clones of each other and rarely if ever mutate, so no ant since the beginning of antdom has ever been mentally ill?)
It does make you wonder.