The argument seems a bit myopic. The author is talking about errors and vulnerabilities found in libraries while ignoring those same factors in bespoke code. At best that's a "security through obscurity" scheme.
It is about trade offs. Is the time/money saved and the additional features gained worth the cost that some of features you don't use may result in more bugs that affect you in some way. For the most part I'd say no: I can write my own whatever, but that too will have bugs, and I need to fix all of them. I work with people who disagree with me on this one, and so we have a lot of pain maintaining code we wrote ourselves that isn't as good as a library I could have downloaded. Or in some case code that is already on our system - We have 6 different logging frameworks in one project, 3 we wrote in house, this is a big mess.