You don't need to reinvent the wheel, but you have to know how it works.

I do suppose that people who have built their own computers and have used multiple operating systems have better knowledge of how computers work…

Of course.

And your code will show you how that wheel will break into very little pieces

Sometimes it's even better to reinvent the wheel, if existing wheels aren't easily serviceable. Other people's wheels are often unnecessarily complex and don't fit properly, because they weren't designed for your vehicle.

I think everyone knows the scenario where a package keeps you from upgrading your framework, so you fork the package, fix it, and wait for your PR to be resolved.

Then you realize that you really only use one single function from that package, and it would've been so much easier if you had just written those 10 lines into your own codebase from the start.