What should I be doing differently?

So I just went through a game where I went 17/5 on Twitch but my ONE teammate intentionally feeding lost us the game. He won’t be banned either because Riot obviously doesn’t want players to rank up I guess but I’m just curious, how does one rank up when you can do well but your team is actually the reason you lose. I’m not a great player don’t get me wrong. I’m no god. I do well in 6/10 games I play but I lose waaaaay more than I win. I can do well but I usually have one teammate that just loses us the game. Whether it’s them inting(they never get punished for it though) or its that no one knows how to peel in low elo. Maybe I’m wrong. Maybe I’m absolute shit but when I do the most damage and die the least but can’t win I feel like that an issue.