I've been learning this recently.
I'm in normals, was 116-102 (which included lots of losses when I was learning the game) until an 8 game losing streak now. I was regularly the only non level 30 on the team, and matched with all gold and plats, occasionally a high silver. Now I'm matched with bronze and lower level players. Can't win no matter what. Go adc, the support goes aggressive when we're behind in Lane. Go support, the adc goes aggressive when it's a late game carry. Go jungle, lanes constantly asking for help when I'm on the opposite side of the map trying to farm my jungle (I'm not playing an early ganker). Last game I finally got mid, top said he couldn't handle kayle so I offered to Lane swap, go 3-0 in Lane so the total kills are 3-15. Then I get 3v1'd by their fed jungle and mid and get a kill and escape, basically proving they weren't even good my team just sucked.
Not sure what it is (and sorry for ranting). Didn't mind losing the first few games, figured it was a matter of having not played much for a while and the new jungle, but once I've dropped enough... seems hopeless