I'm not really against moving off the word I just feel a bit odd about it. Like you point out.

I think with anxiety there's a small difference in that it's never used perjoratively. Whereas narcissism is. But I agree with you that if anxiety can be used descriptively for a type of behaviour without meeting the standards for it being a disorder narcisisstic behaviour can be the same thing without meeting the standard.

In the same way anxiety could also be replace with "uncomfortable" or "scared" but this would not be as strong in tone, not really describing the seriousness of the emotion. In this same way narcissism shares that.

Again though, not really a hill I'd die on or anything. It is certainly overused for even incredibly minor things at times.