Solo Q is a blessing and a curse. Its great because it lets normal people play competitively and feel competitive without finding 4 other people for a team. But its a curse because you dont know any of the randoms you get matched with and their goals/what they are going to do. And, the game is so snowbally and team-focused, they affect your game far more than say, solo Qing in CS:GO or Overwatch or something where your aim will carry you. If your mid feeds kat 5 kills, your game is probably just over if you are Ashe or something. There seems to be far too many people who Q ranked with little care of winning or trying. They are tilted from last game, from previous teammates, etc. Just a cascading system of randoms who just don't give a fk at any given time. Its like how Traffic starts. Sometimes it starts just because a few cars slowed down. Your shit-show of ranked teammates started earlier in the day when one team got a troll, which spread like a virus into every other game.
I dunno, I only Q ranked to win. So i feel your pain when you constantly get people who don't. They want to troll, they want to lose, they want to ruin other people's fun just to be that person, and revel in others' misery, etc. These are the people who will deny trading you in ARAM to reroll the champ away on purpose. Just those kinds of people. Nothing you can do but just write those games off and try and not let it ruin the others, which is hard because these dudes exist in damn near every game.
Every now and then you will get taht good game. That one where everyone is trying to win. You or the enemy team doesn't have some troll picker/thrower, some guy raging 35 minutes in and throwing on purpose to "teach you a lesson cause you don't deserve to win," and you see how good League could be. And then next game you get a guy banning your champ and insta locking Teemo support and tower diving at lvl 1.