So it was more or less a large solo project? How do you know your code base was much better than those less clean/spaghetti codebases? Your own code is obviously easier to read/understand than that of others. In general it's easier to write code than to read/understand code of others. Developers who are founding members of a codebase are able to navigate it better vs those who come later and therefore able to work much faster. It may give them a false impression that they are genius 10x coder. Then when developer who comes later is not able to be productive, founding developer would blame it on incompetence of newer developer. But it could also be that codebase is of poor quality, but as founding developer you don't see it. It's hard to be objective about your own code. Now let's go to the reverse situation when you are spending hours "tracing state through spaghetti-like code". It could in fact be that it's actually a great code written by a 10x developer, but you are not smart enough to understand how it works. It's natural to blame someone else and not you.