Just check any mature project's commit history. It's rarely that huge, even for things that brought in features. Here's a PR[0] that's less than the usual rambling ChatGPT produces, and add a valuable feature to the software. More often than not, you spend more time designing the feature than actually coding it. And a huge part of the design process is dealing with impact to other parts of the project.

[0]: https://github.com/OpenRC/openrc/pull/723/files