IMO poor structure of a codebase is a sign that there is a culture problem. You acknowledge that there is an issue but have dedicated no resources to solve it.

IMO poor structure of a codebase is a sign that there is a culture problem. You acknowledge that there is an issue but have dedicated no resources to solve it. The way to fix sloppiness is to break your bad habits for new code, and then fix the issues with the old code over time. My recommendation would be to begin adding tests to your code, keep files sizes manageable (under 120 lines), keep functions under 7 lines. In general just be a professional instead of running around trying to fight fires all the time. Luckily 15k lines of code is a pretty small project so you aren't completely screwed.