i think there is a limit though if i recall ( i remember reading it somewhere). For Lol, it wont match you outside a certain ELO range if im not mistaken
I have not played LoL in a long time, but back in Season 3 (with the new ELO and tier system) you got matched with players close to you skill level, but if it took too long, you could still get matched with players with higher or lower ELO, but the penalty and reward for losing or winning was different. If you could manage to win a skilled team, you got more ELO, and if you lost to a total noob, you lost a lot ELO. But it all goes back to the mega huge player base.