Actually, the point is not that Nix is bad (though there are reports of packages installing things you didn't want because someone thought a dependency of the root package might need it). It's that the author doesn't have enough experience as a sysamin to speak on Nix actual strengths and weaknesses when compared to tools they don't appear to understand very well.

This article is fluff because of this lack of experience; it honestly reads as another "looks at this cool thing I know nothing about!"