I would say the main takeaway from these lists is: Use a library where the library author has a much bigger vested interest in the edge cases than you do.

Don't implement date and time calculations yourself, just use the library, even for things like "add a day".

Don't parse addresses yourself, use a library. Don't validate email yourself, use a library. Don't validate input yourself, use a library.

Unless the runtime or memory space is absolutely critical to your application, using a library won't make things noticeably worse.