[memset]

I would suggest taking some time to evaluate what, specifically, you are observing that leads you to believe you are a terrible developer.

Your one example is interviewing and OOP. This is a specific skill that you could practice: by reading, perhaps some memorization of terms, or even trying a side project with an intentionality of implementing in an OO way.

What are other things that you would like to be able to do, but feel that you are unable to? That can serve as a starting point for things to learn.

Bear in mind that there is no clear definition of a good or terrible programmer. The good ones are perhaps fast, or have deep knowledge of systems, or have wide knowledge of many types of technologies, or can write very fast code, or have a lot of expertise in an industry, or none or all of the above.

A good programmer is characterized by a set of skills that make them effective in the role of building things that are valuable to users. So the exercise is to try and identify those skills, and from there you could find ways to develop them.