I don't think you should quit, you just need someone to show you the way. League is a game that requires a decent amount of Mechanical Skill (earned over time), Knowledge (Earned at your own pace depending on how much you study outside of the game), Common sense (again, earned over time), and the ability to put the team's needs before your needs (More of a good character trait than a skill). The first thing I think you should do is expand your champion pool. Get out of your comfort zone and explore all of the other champions and roles the game has to offer. It won't happen in a day, or eve a week, but after a while, you'll notice that things you struggled with before become second nature to you, and you'll find that things you had to think about before doing become split second decisions that you make based on quick judgements from a glance of the situation. Give it time, I'm sure you can improve