I am major in computer science, and published paper in top conference. Tree traversal is trivial for me. So I guess I have decent CS background and knowledge?
Writing bug free and perfect code is not equal to simply solve the problem. If you have prepared coding interviews (especially for new grad and internship), you should understand it is less about knowledge but more about practicing and memorization for that specific purpose. The time spent on it is almost a waste in the future.
If the interview is knowledge based or problem solving oriented, I am all for it. Sadly, it is not today in many places. And that is exactly why website like Leetcode exists.