All it is is people not realizing that they aren't actually playing better than the people at their rank. I go 10/3/8 every match but I just can't win because of feeders!
Except they don't realize how often that they go 2/8/3, and how they don't actually know how to win when they're 10/3/8. They don't realize they just go through the match on autopilot without ever taking the reigns and forcing that match to become a win.
But it's always the system holding them back. They're just getting unlucky.
If you just keep in mind that these games are becoming hard because you don't understand how to win better than the people that you're playing with, you should play ranked because you're going to naturally look for ways to improve your chances of winning, thus getting better. If you think you're going to get stuck in a bitch-fit rut about how your team drags you down every time, don't bother.