"What do I do?"
You just have to suck it up and carry the games that you can. Ultimately, RIOT can't stop players from AFKing or feeding or trolling. If RIOT could, then they probably would have already implemented that feature. And if RIOT can and isn't, it is because they don't want to or don't know they can.
"Why has RIOT perpetuated a system that allows this to happen?"
This is actually a really good question. Every season is the same story, the boards are inundated with players complaining about placements. Let's have some history:
RIOT used to openly use an ELO system. ELO systems are designed for single player games (in particular chess) and not intended to "reset" every season.
In the classic ELO system a single game between two 1000 ELO players can net one player a new ELO of 1400 and the other a new ELO of 600. If you're thinking that that's just ridiculous, then you're absolutely right. It is ridiculous. And so they developed a K-factor that allowed you to earn fewer and fewer ELO points the more games you played, typically K = 800/(#games). So after you play 100 games, your ELO might only move 4 points for the same win that initially gave you 400 points (or something like this).
But RIOT resets every season (something ELO wasn't designed to do). And therefore, every season, we see the same story. There are players who literally wait until later in the season and only play the ten games to see if they get a Silver placement because the chances of getting the Silver placement are actually reasonably good - you don't have to be particularly skilled, you just play the system and maybe get lucky.
History lesson over, why does RIOT keep their particular variant of this obviously flawed system?
Because RIOT doesn't have anything else in mind that they think would work better. Games everywhere implement ELO systems like it's the only legit way to do competitive gaming. ELO has been enshrined in the minds of gamers for so long that it's actually hard for them to think of a different better way of doing things. Even when RIOT implemented the League system they secretly kept their own matchmaking system behind the scenes that basically acts like an ELO system. We just don't get to see it.
"What can I possibly do to improve myself?"
The good news is that you aren't the first player to be in this position. Many, many other players have been in this exact same situation. There are plenty of guides on how to improve your game. You might be thinking that it "happens every game" which is pretty close to the truth, but ultimately not really quite true. And it's that not really quite true part where you really need to make a difference and win.
Good Luck on the Fields of Chaos and Humiliation Justice?
