Okay, I have a challenge for you. Take a bronze 5 Annie, put them against Annie Bot(The player). If Annie takes 0 skill to play, then the Bronze 5 Annie will win 50% of the time, since they are on an even playing field.
Oh, what is that? The Diamond/Challenger/Master players are still beating the bronze players on 'skilless' champions? Even with the exact same build and gold? Damn... it's almost like they're utilizing the champion's strengths, weaknesses, design and mechanics better. To strategize against their enemies better.
Hate to tell you, but until you have literally maxed out the potential of the game's engine on how your champion can be refined with a perfectly calculated build and absolutely omniscience over what is happening in the game with perfect decision making. Then you haven't reached the peak of potential for your champion.
As long as a Diamond Garen player is better than a Silver Garen player, then he isn't a skilless champion.
League is very easy to pick up, hard to master in general. And only a few select individuals have mastered a couple specific champions to nearly their peak potential. But maybe if you are losing to Annie on Syndra, maybe you should try picking up a champion with a skill floor more suitable for you :^) rather than complaining that other people's champions "Don't require any skill!"