I'm a Plat 5 scrublord seeing how far I can climb :P My game knowledge and game mechanics both need a lot of work, but I've already started to notice a recurring pattern of silliness in high Gold / low Plat (it may or may not be present elsewhere, idk), and that is that many people enter a game absolutely determined to play a situational champion regardless of what else happens in champ select.
Many of these people climbed out of low Gold or even Silver by maining this champ. They often respond to skepticism - truthfully - by saying that they can make it work. But the major problem with faulty comps is that you feel like you're doing well right up until you lose, and even then it often doesn't feel like you made a mistake. The primary culprits that I've seen are things like Twitch or Tryndamere jungle, Vayne top, and just about every champ "support." Am I saying that these champs should not be played? NO. Don't be a meta sheep and play only things that are "good," but don't just play whatever you want all the time either. When you're the third, fourth, or fifth pick on your team, you need to seriously think about what your pick needs to bring to the table. Yeah, maybe you can play Quinn top, and maybe you can even win lane with it, but that may leave your team without hard CC to lock down the enemy Yi later in the game. Maybe you're the best Twitch jungle NA, but if your team doesn't have a frontline and you're last pick, you may wanna save your hypercarry fantasies for next game.
Often, it's easy to overlook comp when analyzing a fight. At the end of the game when you lose that crucial teamfight 5 to 1, many people blame each other and abstractions like "positioning" and "focus." These are absolutely critical components of a fight and can indeed make you lose them, but be aware of reasons for your loss that could've started half an hour before the fight. Before you pick a champion, understand what your job in that game is, and decide who in your pool best fulfills that role. Your team thanks you, even though they'll never actually say it because we're all toxic.