Humans have a very limited amount of working memory. 3-5 items on average. A savant might be at something like 12. It is trivially easy to blow that with code. OO with code inheritance is a prime example of combinatorial explosion that can lead to more possibilities than atoms in the universe, let alone one persons ability to reason.

Watch ‘Simple made Easy’ by Rich Hickey; a classic from our industry. The battle against complexity is ever ongoing. https://youtu.be/SxdOUGdseq4?feature=shared