Hmm, I agree somewhat with both your comment and the one you're responding to. However, the claim that you should read the source of the libraries/frameworks you're using to me is interesting - because to me it seems sane, however not always entirely viable.

For example, who would be more successful:

A) A Java developer who reads the Spring source code and dives into that verbose Eldritch codebase with years upon years of fixes, design patterns and abstractions, all to learn how the dependency injection works better, probably spending days to weeks in the process?

B) Or perhaps someone who looks up the annotations or configuration they need, or maybe other code snippets on StackOverflow or the docs, or a similar site and solves their problem so they can move on to the next tasks, while being none the wiser otherwise?

Sometimes the answer will be A (deep knowledge can be useful), sometimes it will be B (we all have limited time and energy), however it feels to me that with sufficiently complex codebases one might just get more and more confused as well, as opposed to gaining any sort of a clarity or understanding, when the framework/library actually abstracts away really complex things.

Just using Java as the example here, as it's one of the more enterprisey languages and Spring as an arguably brownfield maintenance mode framework that's huge, given its long history.