On the surface it seems simple, but it is actually very complicated when you combine all the factors that go into winning a match. Runes, masteries, champions, summoner abilities, starting items, item builds, lane matchups and counters, team fights, ward control, dragon/baron objectives with timing/defense, taking down towers, ganks, jungle timers and ganking paths, ability combo's, roaming, farming cs vs kills vs defending objectives etc etc etc.
When discussing RTS' and RPG's I always like to refer people to this diagram I found which perfectly explains how I view these types of games.
http://thefuntimesguide.com/images/blogs/rockpaperscissors.jpg
The system itself is NOT complicated, developers have just made it so complicated they don't know how to balance it and never will, why do you think they come out with patches so often? If these games were balanced they wouldn't need to patch them constantly. RTS' and RPG's are just essentially a complicated game of rock/paper/scissors, which is why I don't like them, want to prove me wrong? Use mathematics, instead of foaming at the mouth like everyone I've talked to about this does who defends these games.
This is why modern FPS games feel so borked as well at times, it's because the developers have gone and made the damage systems etc. extremely complicated, this isn't much of an issue in singleplayer or co-op as you're just up against NPCs but it's a major one when you're playing a multiplayer game and want all players to be equal and for it to all be about skill.
Play the game, become a Challenger (meaning you are one of the very best in the world) then come back and tell us how uncomplicated it is. If the game could be boiled down to a simle mathematical formula THAT would be uncomplicated, good luck creating one.