I think the problem that a lot of people have, PogoPogoPogoPogo included, is that they think of player skill as a sort of number that gets summed over a team in some way to determine who wins. The team with the highest total skill should win, they reason, so if your skill is higher than average for your elo, your elo should slowly rise.
The problem with this is that, regardless of elo, there are few teammates so bad they usually lose; if they were that bad, their elo would drop further, and you wouldn't get matched with them. What I've found instead is that a lot of low-elo players are relatively bad at playing but surprisingly good at carrying. That is, they've honed a particular playstyle enough to snowball into a raging death machine if things go their way, but if they get countered or make an early mistake, they stick to their rigid, aggressive tactics and quickly become worse than useless. I think Asellas's comment is rather telling:
You can carry a game very well, and than again not get a kill the next game.
At higher elos, this isn't normal; one may carry some games very well, but unless one's assists are through the roof, going kill-less is usually a sign that someone made a serious mistake. In elo hell, though, this sort of "bipolar" performance seems fairly common.
So what's the upshot? When so many players are walking a fine line between awesome and abysmal, the winner stops being a question of "which team has the most total skill?" and starts being a question of "which team has the bigger snowballs?". In this setting, it doesn't matter if you get a kill or two, keep up good cs, and take down your tower, because the winning team was already decided when one of the adcs went 6/0 by 15 minutes. If anything, playing a cautious and flexible game can slightly decrease
your chances of winning, because your team has one fewer potential snowball. This also explains why gold-and-above-level players tend to deny that elo hell exists; if you're so good you can not only adapt to but reliably dominate changing circumstances, you can snowball against an inflexible player nearly every time, and elo hell becomes easy to escape.
Sorry for the wall of text - I've been pondering this for a while. Since putting my finger on what I think the problem is, I've made an effort to 1)always choose a champion well suited to 1v1 and 1v2, 2)never play support if I can help it, and 3)focus on helping my teammates win their lanes as much as I focus on winning my own, and I seem to be slowly but steadily regaining my lost elo.