And sadly, that's why it's so damn flawed.
There's a reason why most MOBA matchmaking systems take into account level/time played as well.
DOTA 2 takes into account hours played and matches you accordingly - the only exception is if you've flagged the smurf protection system. HoTS tries to match level 40s with level 40s, though it does falter due to the fact it's taking into account a tonne of other variables like hero role selected and elo. Smite matches under level 30s with under 30s, groups not withstanding. I've never played LoL, but wouldn't be surprised if a system in that exists as well.
Levels don't mean skill, but they do mean experience in the game. Even worse, in this it means heroes, and also more importantly the likely hood of having better equipment.
Levels shouldn't be the only thing being taken into account, but it damn well should be taken into account when matchmaking. Without, you get a lowbie winning a game and getting a massive boost in ELO (due to how systems give increased points when uncertainty is high), which puts them in matches with better more experienced players which they shouldn't be and makes it totally lopsided.
