This assumes that I could implement something as well as the maintainers of the library I use. I agree that something trivially should be implemented on your own, but if there is special knowledge required (the obvious example is cryptography, but also something like HTTP requests) I rather rely on a widely used library than my own code that I now have to maintain and check for security issues instead of just updating the dependency version whenever a CVE is published.
Also if there is. A client by an API provider for my language, why shouldn’t I use it instead of rolling my own?
Another example is a framework like React or Angular or Svelte, which brings along a whole lot of dependencies. Sure, I could not use something like that and write everything from scratch.
But where is the value of all that code to customers? If I want to roll my own HTTP server up from the sockets, I can do that as a play project. But not using libraries for a real world project to solve business needs is a bit of an odd take.
Anyways, that’s enough of a rant. Have fun in the replies. 😎
Oh, I forgot one thing:
This sounds like you want to prove something. That you can do it better than the maintainers of the library. That you can solve hard problems on your own instead of relying on other people.
That’s all great and sometimes it’s good to do hard things on your own and make sure you could do it just in case. But it’s not always necessary to do everything yourself and learn every lesson yourself. It’s a valid way to build on knowledge and work of others to achieve your goals.