i dont really like that either, and hate to be hypocritical, but sometimes it really is true. Im mid gold, so this really doesn't happen, but in_ really _low elo like silver and bronze, sometimes the teams really do hold players back. Even playing on an old account I used to use (when I first started playing), the teams just simply amaze me. One game I had Kogmaw, Thresh bot. Kogmaw went mixed and they both took smite and obviously fed, like hello??? play normals.
The only reason I've had some success with trying to get the account raised a little, is literally because Im a gold player and I can pretty much just hard carry. I simply dont see a way where a bronze/silver player could actually carry an entire team if they aren't _that _much better than the division they're in (but still decent enough that they actually do deserve to climb a rank or two)
Its kind of unfortunate honestly, and really not that fair to lower elo players.
However, people in like gold/plat+ really have no right to say their teams are holding them back, because its not that often that they'll have a teammate thats simply there because they were elo boosted, so if they can't climb its pretty much their fault.