ranked 5s matchmaking

im in a ranked 5s team and we have 4 silvers and 1 plat, we usually play against diamonds/plats/golds. why is this, it makes it frustrating when you play people 2-3 leagues above you who obviously have more skill. Also we are silver in ranked 5 only. we are 7-3 but the games with diamond carries are almost impossible to win.