it's as I said in the second (now third, with the edit) paragraph. some games are unwinnable because they're stacked. but not all games will be stacked against you. the worst case is there are two good players in the room (including you) and the other good player keeps getting on the other team and just carries that little bit harder. but this isn't what I'm getting at here.Like I said before, this kind of logic is silly. While one extremely good player is nice, even he/she is going to fall under the weight of FOUR extremely good players. I'm not saying everyone has to reach the height of squid perfection, but this whole "just get good" attitude doesn't solve every problem you're going to have in a game about team play and map control. If my smartest option is to not do anything because the team isn't good enough, and the option you provide is "just get good enough to do everything"...
if a player says that they're carrying every game, then they should be winning enough to rank up. it's not any kind of wild logic, it's just how luck works. luck very quickly balances out, so a player who is actually carrying (and not taking important defensive positions that inflate their k/d) should be winning enough to rank up (or at least not losing enough to be demoted). for every loss due to a bad team, they should have a win as a result of a good team. every other game, where the teams are not so stacked as to be uncarryable or unthrowable (let's just pretend these are actual words), they should be winning enough to be promoted. if they aren't, then they aren't carrying as much as they think they are, and maybe lack in some area that is not immediately reflected by k/d.
I've edited the OP to hopefully clarify this.