Over half my gold ranked games this season have had boosters in them.
I've played about 80 games so far on a couple accounts trying to get platinum but I'm about to just quit. Not because I won't get there but just because these games are never enjoyable. I'm not joking when I say at least 40 of these games have had obvious boosters in them. And most of the time those boosters are premade with other boosters. I've even had a couple games (2 or 3) that had at least 7 boosters in the game, all the way up to games with all 9 other players being boosters.
Combine this with how many games snowball out of control this season due to poor game design or matchmaking, and you're lucky to get even 5% of your games to be enjoyable, close games between evenly matched teams.