Those are two well-known approaches to problem solving: GP is proposing top-down, you're advocating for bottom-up. There are pros and cons to each, and in the end it is more of a matter of preferences.

Just to give an example of someone else advocating for top-down problem solving, Bjarne advocates strongly for designing the libraries that you will need before writing specific code for your problem. He has some example videos where he goes through a code review taking some piece of procedural business code and showing how it should have been written to take advantage of existing libraries and creating new ones before.