In my promo game to Plat 2

I go support. I have a 70%+ winrate as support. Last game in my series for promotion to Plat 2 and I get a Silver 2 adc Caitlyn. He was absolutely awful. The poor guy got absolutely stomped apologizing and getting flamed by our teammates. But its not his fault, WTF is he doing in a plat game? WTF is this matchmaking? I know Riot doesn't give a crap about our feedback because they are deleting the boards but WTF!!! I shouldn't get a Silver 2 player in my team in my promotion game to Plat 2.

Edit: My team: Gold 2, Plat 3, Plat 3, Plat 3, Silver 2

Opponents: Plat 2, Plat 2, Plat 2, Plat 4, Plat 3

How is this fair?