Like with any skill, practice helps. It sounds like you dont really care that you dont do exceptionally well at interview. But if you wanted to improve that skill you could focus some time on it.
Think of another skill you only use once every year or two. You are not going to be fantastic at it. I've played a lot of basketball in my life but only play in games ever year or two when I happen to be with folks who have a regular game. Now I'm in pretty decent shape so in general I do okay but the actual skills of playing basketball are rusty so I'm going to be a 5-7 out of 10. If I played basketball everyday I would probably be a 7-8 out of ten.
The same goes for interviewing. You are coding regularly so you have some of the prerequisites for doing well in interviews but without practicing typical interview type questions you will not excel at them. If you did 100 interviews over the next year I'm sure you would start to see patterns, improve on your weaknesses, and be closer to a 10 than a 5. It's a skill you have to work on outside of just coding if you want to be a great interviewee.