Ranked Matchmaking is horrible.

I have been playing normals for a while and i usually get teamed up against and with gold and plat players and everyone does well and seem to understand their champs and what to do at certain points in the game. Nobody is raging and everything goes smoothly. after i got runes and the champs i like to play, I decide to try my placement matches. Wow. The players in ranked are awful to play with, they only rage and blame each other and don't even have a clue what they are doing themselves. Everyone of them gets stomped in lane. It seems like the skill level is disproportionate between players for both allies and the enemy team. Also, I couldn't select a specific board for this, it was only help and support available.