Bad luck or bad system ?

You ever felt that after you get ''unlucky'' 2 or 3 games that next 10 are gonna be just same ? Well i have, how comes that no matter how you play these games will be unwinnable, the God himself will make sure you lose even tho you are 20 kills ahead But when you start winning you can play like garbage you're still going to win. Riot has some weird pattern of bullsht and grinding feels like hell, can't be so random because after hundreds of games i can see that bullsht clearer every time.