I agree with the idea in theory but the generalization is faulty. There are many people who achieved success BECAUSE of writing. For example, JK Rowling is known because of her Harry Potter books and not because she was successful. Her life before that was very non-description. Sylvester Stallone wrote a screenplay first and then produced a movie. That was what brought the success or at least the recognition that catalyzed the success.

There are many other examples.

But I get it. Don’t just write a book and expect success to come. Do something.