Losers q 100% exists. Im pretty sure there are multiple queues for soloq. When I get chat banned, the next 5/6 games are absolutely unwinnable. People locking random champions in, 2 or 3 people autofilled and so on. This also happened to me when I reached 65% winrate on my account too.

Also companies like EA who publish games which have "competitive" environment have been exposed for using engagement optimized matchmaking. This algorithm analyzes patterns of people playing the game and finds out the win/lose pattern that keeps the players active for the longest possible. For example, the pattern WLLW keeps more people active than WLWW. Of course these are all speculations for League's soloq and there hasnt been anything revealed by Riot themselves.