Matchmaking is unfairly biased against skilled players (normals)

I have been playing LoL frequently since season 3, and recently I've begun to notice a trend in my games since I've taken steps to improve as a player. I only play normals since I can't stand the toxicity of ranked and don't have the time to grind enough games to attain my real rank, but normals have become a terrible experience for me. I don't know why, but in well over 50% of my games (I would estimate somewhere between 60-65%), my teammates end up matched against players well above their skill level. This means that I start most of my games at a huge disadvantage since I can expect my teammates to feed. I don't know how the matchmaking system works, but it feels bad to go into games with the expectation that my team will not perform at the same level as my opponents.