If you have somewhat flexible time frame for a project, it can be a good idea to reinvent the wheel.
Libraries and copy and paste code is perfect in many ways. It's often the choice you should make in deciding how you're going to develop a project.
Yet sometimes. We have a little more time. If that ever happens and you get the chance to roll your own; try it. It'll provide insight into...
- The real worth of code you inherit by default from those who share
- How well the solutions you use are coded (more functionality than style).
- What features the code you use is missing (giving you chance to perhaps send in a PR for your favourite repo of choice)
And likely many more.
Rolling your own forces you to understand the code your write and use. It's a great experience. So if you have the privilege of time and opportunity to do so. Do it!