That's going to be true to some extent of every library your company uses, but for every library someone writes and offers as FOSS, you don't have to spend the cycles designing, developing, and maintaining your own, nor training new hires on using it. You're fundamentally misunderstanding the value of having good quality tools developed by someone else.

And I'm not even going to _start_ on what I think of your attitude towards test tooling vs "central libraries" other than to note that if you don't consider test tools central to your development process, I think you have bigger problems.