I think it has more to do with primarily only having experience with code you wrote yourself or a small codebase written by yourself and others. I have a tongu

I think it has more to do with primarily only having experience with code you wrote yourself or a small codebase written by yourself and others. I have a tongue in cheek saying of "If you haven't maintained code written by others then you probably write code like an asshole". You learn a lot about what never to do by working with very large (and/or very old) codebases that you yourself didn't design. Also, to be fair to the people that did design them, even your greatest most beautiful design will look terrible to some people, and likely to posterity.