The leader doesn't like me sending him messages all the time. I don't contact him anymore. I just asked him for a happy new year. He responded to me warmly. What does he think?

He didn't think so much. He should still be polite to his friends. He should always say something when he is polite. It's a bit unreasonable to ignore it, let alone leaders and subordinates. Even people you don't know should reply politely when asking for a happy new year. This is the most basic principle of being a man.