In my experience, senior engineers without the curiosity to occasionally dig deeper into their frameworks are significantly worse engineers. No framework, library, or language is perfect. A big part of your job is understanding how your code will execute. Sometimes that even requires, at a very high level, imagining how that code will compile down to assembly once you strip away all the abstractions.

Eventually you will get a memory leak even in a GCd language. Eventually there will be some incredibly obscure, unreported bug in a library. Eventually you will find an issue in unmaintained code you depend on. Eventually there will be performance problems caused by too many layers of abstraction.

You either need to know, roughly, how your dependencies work by occasionally digging into their code/reading the documentation. Or you need intuition to know how it probably works, but you usually build that intuition by actually writing/reading code.