PLEASE FIX the match making system for players in Placement matches.

A little background, I'm New and been playing league for 2.5 months. I'm a competitive player and only plays ranked. I've slowly worked my way from low silver to low plat now. I just had an game today which is almost causing me to quit and its people like me quiting thats going to bring this game down. Anyway I was in a high-gold low-plat elo match and I'm support with an ADC who was in his FIRST placement match with NO prior ranked experience. Suffice to say I could immediately tell from his laning that he was a bronze level player. Obviously as a new player playing his first ranked, he died immediately, then just left the game 4 minutes in. The four remaining players tried our best to last but with one man out it proved to be too difficult, but it was clearly a game if we had a similar elo adc we couldve won. I want to know WHY riot thinks its a good idea to put first time Placement players in 1690 elo hi-gold matches? Not only is it a bad experience for that player, but everyone else on the team. This has happened 3-4 times already which just cost me games for no reason where Placement players are put into my high-gold games. Why can't match making put new placement players into low silver and if they keep winning, move up from there? Putting a new player in high-gold makes absolutely NO sense and ruins a game for the rest of the team. This has happened enough where I'm considering calling it quits after 2.5 months. And I wont even get into the blue essence issue of playing 500 ranked games in 2 months and still only have 25 champions because essence take days to collect to buy new champions and I cant afford to drop $100s to buy champs. I hope RIOT reads this and considers my feed back as a relatively new player who may not stick around long.