So, here is the thing.
There is a balance between "dig into this yourself" and "ask an expert in house". If you spend a week trying to find the source code, you've clearly gone too far. If you ask a question about every function, you've gone too far in the other direction.
The problem is, this is a balance that people find *by* working in professional environments, it isn't something that gets taught in school, so far as I know.
This is why entry level engineers are basically a loss early on; a big part of the ramp up is how things work in a professional environment, not just "how we do things differently here". Better companies know this, and the manager will either mentor the engineer, or assign a mentor. Worse companies, well, leave you to sink or swim.