If you're consistently queuing in their games technically you're elo boosting them just by being there.
Communication in a trio / quad queue also has a noticeable affect on gameplay. Match making isn't so good at not matching 3's or 4's against pure solo teams.
All games are mostly knowledge. It's just some have more simplistic or easily executed mechanics than others. (Physical requirements for playing Chess Vs Starcraft is a good example of this)
Luckily league mechanically (Physical requirements) is relatively simple for a good portion of the champions. It's not as demanding to be competitive as other games like Starcraft(Continuous rapid timed actions) or fighting games (Long combos that must be executed absurdly fast and sometimes frame perfect reactionary actions are required to compete).