How does matching with people in placements work?

Hello, I would like to know, how does the matching system in my placement games work. When I am unranked, and I am playing my placement games, my matchup is full of higher elo players, such as Gold or even Platinum, so it is impossible for me to win. Im not trying to be that guy who still complains about his team (even though it is pretty sh*tty :) ) and I know that I don't play good, but I still don't understand the system of matching up people in ranked placements. Can anyone tell me which sense does that thing make?

Thanks to you. :)