I hate the SOLID principles. Especially that they're called principles when they should've been called design patterns at best. In our era of multi-paradigm software engineering OOP is nothing but a tool among others for structuring a program.

Designing all classes in your software to be "extensible in the future for new business requirements" is such a useless (and in most cases, harmful) goal. The number of classes and interfaces should be kept to a possible minimum. In fact, the number of lines should be kept to a reasonable minimum. Rewriting code is good. Refactoring classes to be more generalized (when it actually is needed) is good.

These so-called principles are such newbie traps and they go against the only principle in software engineering, the only law of the land that I recognize: your code should be simple and readable.