Riot why does this happen ?

in my promo to gold V i get a first time karthus , and that match it was his first ranked match he ever played ( unranked ) So you are thinking that someone who just started playing placements on his first account is on the same level as high silver - low gold ? fix your matchmaking , that wasnt a fair match zed snowballing so hard and our karthus was so bad , not even listening to our advices running around the map doing nothing , 40 cs in 15 mins