Egotistical, manipulative, selfish, arrogant, rude, uncaring, abusive, ignorant, mean, bully, evil, entitled, etc.
Look at all these words english offers that are better than calling people narcissistic. More precise and not demonizing a mental health disorder.
For example: "The current American political party is egotistical." "My ex was manipulative and abusive." "That person is arrogant."
The argument that "narcissist and npd are different things" is not necessarily wrong, the two are largely and commonly used separately, but that does not change the impact. When we normalise calling abusive, rude or harmful people narcissists it sets a connection in peoples mind. When a PwNPD reveals to someone that they have npd that person is likely to immediately assume that they are evil and abusive no matter past experiences. Demonizing disorders through everyday language ruins lives.
( these words are not synonymous with npd, they just actually give better explanations than calling people narcissists.)