At this point in many stories many twists are something you'd expect knowing the genre and having seen/read many similar works. So I'm often interested not in what will happen, but how, and if the autor can make it logical and interesting. Like, you always expect shounen MC to win, but when it's executed beautifully, it's amazing, when it's full of BS, you stop enjoying the story. That's my beef with most of shounen stories, in the beginning the characters have certain limits and have to fight smart, in the end it's just hax OP abilities against other hax OP abilities. I really liked Luffy vs Crocodile a lot more that Luffy vs Kaido, same with Sanji vs Absalom vs Sanji vs Queen. I don't remember fights in FMA now, but I liked the consequences for some of the characters, e.g. Roy, and also some of the plot twist were still surprising for me (Pride lol). With OP I gave up on plot twists, but I like it's lore. That's why I like Egghead arc, but the traitor plot seemed really unnecessary to me, especially after so many traitors previously.