You aren't being shafted by Matchmaking

Mathematically the other team has a greater chance of having a feeder or troll on their team then your team does (assuming you aren't one).

It is human nature to only remember when you get trolls or feeders or unwinnable games then it is to remember when your ADC carried you or you won by 30 kills and 6 towers. You generally remember the bad over the good and thus it appears to be more frequent.

The only constant in every game is you and that is the only thing you can change.

If your ADC went 2-11. What could you of done to stop that bot lane snowball or help his lane? How could you of carried better? Could you of used TP to help that lane?

Stop thinking the only reason you can't climb or win your placements is because Riot is shafting you in matchmaking when you have a mathematical advantage over the other team assuming you yourself aren't a feeder or troll.