I feel weirdly fortunate I came up working on open source CMSes in the late 00's --- the docs were typically woefully inadequate, but it taught me to read source and then drop debuggers and trace to confirm my theories about how the source behaved. Often when I see programmers hit a wall, they are for some reason stuck on poking at the underlying code like a black box instead of just trying to understand it. And understanding complex code is hard intellectual work, but to me it's always been more fun than the guess and test of pretending the source is closed.