Absolutely this. It's not a trait that should be measured on a spectrum; it's more like a consistent mode of interacting with the world, a pathological mechanism/system of functioning. It takes a clinician (or victim) some time to see enough examples and gain the experience that's needed to recognize whether any given individual is relating to the world in a narcissistic way.

In other words, it's a pathology of personality, analogous to pathological states of other biological systems. Trying to grasp it as if it was a simple trait (height, introversion/extraversion, BMI) is unlikely to be successful, because narcissism is a pattern of intra- and interpersonal dynamics. It's something that has to be reconstructed from multiple observations.