It really is getting overused. Anyone can have narcissistic traits, but Narcissistic Personality Disorder is a pathology. It doesn’t just mean run-of-the-mill selfish, inconsiderate, dishonest, attention-seeking or prideful behavior. Likewise, I’m sick to death of every lie being referred to as gaslighting. Gaslighting is a specific type of lying, but not all, or even most, lies are gaslighting.
Calling everyone “a narcissist” trivializes the meaning and muddies the understanding of what this disorder is and how profoundly it can damage those who are exposed to it. If you hate your selfish ex, just say so. If your mom is a whiner, just say so. Don’t try to couch it in terms of a psychological disorder that seems “fashionable” at the moment but that you’ve done no reading on and don’t understand. I’ve opened far too many Medium articles purporting to be about NPD that we’re just another rambling laundry list of complaints about an errant ex or miserable parent.