Stop taking the game so seriously. It's just a game.
Ya'll stressing out over how seriously you should take the game and frankly you shouldn't.
Should you play to the best of your ability? Yes. Is it because you're taking the game seriously? No you should do it because it's a common courtesy.
Should you troll? See above. Same with afking or flaming.
I used to take League ultra seriously but then I stopped and I've never been happier. Tbh nowadays I only worry about if I'm learning or enjoying myself. If someone flames me, I let it go. If someone threatens to afk, I say w/e because there's always another game.
You win some and you lose some but if you focus so hard on not winning you will never be happy/satisfied.