What do you do when a friendship goes dull and boring?

Like he's nice to me and I appreciate that but I don't get why we're still friends. I can tell it's not healthy. He can be judgy and weird therefore I don't even talk about my personal life in front of him anymore, seriously somethings about me could give him a heart attack 😅
What confuses me the most and makes me endure him is that he thinks I'm his best friend 😔

That's an offline friend btw.