Lots of people use sewing patterns rather than creating original designs because design thinking is a complex learning skill that requires you to think in a different way. Some people are naturally gifted to think this way while others learn to hone this skill through traditional learning methods.
Many prestigious schools such as Harvard Business School offer classes in design thinking because this leads to innovation. More than that, it teaches you how to solve problems quickly. For more information about design thinking see this article in the Harvard Review: https://hbr.org/2018/09/why-design-thinking-works
Decades ago I studied at Fanshawe College School of Design and it strengthened my design thinking skills. Of course the more you practice the better you get and it becomes second nature. Now I don't know how to think any other way.
Here is an example of a design I recently created. It is called Heating Bag with Straps. About 15 years ago I discovered a natural heating pad that was filled with something granular (not sure what) but it was awesome. It gave moist heat instead of dry electric heat. I haven't found another design I liked as much. I own others but they are either to stiff or don't keep the heat well.
So I decided to create my own. The one I make and sell has three channels so the dried rice can move around and form to your body. It is not overfilled, so it is soft and comfortable. And, I've added straps ( a unique feature) so you can wear it versus leaning on it or draping it over a sore body part. A good design idea made better!