My take on that was that rolling your own crypto is hubris, but for all other ready-made libraries it's just about saving time[0].
There's only one person I ever met who thought manual memory management was a good idea, and their code was terrible in lots of other ways besides that, so I can't say I've ever thought about that particular example.
But after a decade or so of "don't roll your own crypro", I've also heard that if you specifically want to get into cryptography, the only way to do it is to research existing crypro libraries and work your way upwards, starting from "can I find bugs someone else already found, without reading the full details of their report?" and eventually rolling your own.
[0] That said, I'd now also add that libraries serve as Schelling points to make it easier to find jobs and to find workers.
There's only one person I ever met who thought manual memory management was a good idea, and their code was terrible in lots of other ways besides that, so I can't say I've ever thought about that particular example.
But after a decade or so of "don't roll your own crypro", I've also heard that if you specifically want to get into cryptography, the only way to do it is to research existing crypro libraries and work your way upwards, starting from "can I find bugs someone else already found, without reading the full details of their report?" and eventually rolling your own.
[0] That said, I'd now also add that libraries serve as Schelling points to make it easier to find jobs and to find workers.