> Part of the benefit over a dependency is that the code added will (hopefully) be narrowly tailored to your specific need, rather than the generic implementation from a library that likely has support for unused features.

In decent ecosystems there should be low or zero overhead to that.

> Not including the unused features both makes the code you are adding easier to read and understand, but it also may be more efficient for your specific use case, since you don't have to take into account all the other possible use cases you don't care about.

Maybe. I find generic code is often easier to read than specialised custom implementations, because there is necessarily a proper separation of concerns in the generic version.