You don't know what my world consists of, so I'm not sure where that comment comes from.
My comment was addressing the general sentiment from the GP regarding the potential presence of bugs in software, not the log4j issue in particular-- plenty if other have done that and I won't rehash it.
And of course your comment seems to ignitre the part of mine where I say that rolling your own version of something can be okay, but it's a decision to be made very carefully, along with my implication that trivial things are a different category. (your printf straw man would be about as trivial as it gets, so you're not making a string argument against my comment here)
And this is not just for issues of bugs, but also time and resources. Why spend your time writing a complex library for something that is not part of the core of your business if a well established OSS alternative that has had countless eyes reviewing the codebase, and it can do all you need? I don't go rewriting grep or other utilities. I don't roll my own equivalent of a nearly decade old library like python Requests. I use well established tools from trusted sources and then get down to my real work.
This is pretty much how most professions go about their jobs: use established tools, get to work. If there's a difference it's that many other engineering disciplines have had more than ~75 years to refine their established processes and basic tools.