All social psych research looking at narcissism puts it on a continuum and acknowledges an insecurity basis.

In psychology there is no longer such a thing as a nature nurture debate. Instead, these all happen as an interaction. If it is just genetics then it would be unlikely for narcissists to appear without parents who are narcissists. It would be more likely to run in families. It is a complex combination of factors influencing one another. No psych prof of any standing would deny this.

Most research currently on narcissism also looks at the cultural effects, especially how it happens more often in individualistic societies and is highly linked to things like social media.

This desire to instead label narcissism as psychopathy is strange. Why are we afraid of admitting we have these traits? Would viewing narcissists as insecure beings bring up too much empathy?

My dad is an extreme narcissist and it is definitely based on insecurity. I don't have to like him, but I can try to understand him.

No one would desperately need attention/approval if not insecure.