It’s not just you, this is a fundamental challenge in programming. I think this paper by Peter Naur lays out the reason why it’s difficult, because software is a lossy representation of a theory held in one or more individuals heads. The original author had a model for how a problem could be solved by written code, and how that code might be extended or refactored in the future to solve related problems. No amount of API design or naming conventions or documentation can perfectly capture those ideas.
https://pages.cs.wisc.edu/~remzi/Naur.pdf