Narcissism != Narcissistic Personality Disorder. A person that lacks narcissism will have a lot of problems.

Actually that’s interesting because logically it implies that anybody seeking diagnosis is in fact impaired.

I never mentioned that a narcissist would seek a diagnosis for their disorder, only that their disorder can be debilitating.

Debilitating to themselves but infinitely more harmful for the people they interact with. Maybe a diagnosis would open them up to some mitigations on their behavior. Narcissism personality disorder cannot be cured but sufferers can learn to do less harm.