I would have really loved it if you had talked something about design patterns. As the code base grows, there would arise a point where you would need to implement the design pattern. SOLID principles itself is an indirect form of design patterns and it's very important while maintaining the code repo.

Yes, refactoring would help but if a person doesn't have the knowledge of the design patterns, the person won’t be able to refactor the code correctly(when needed) and it would definitely create problems in the longer run.