This is why ELO Hell feels real, because in a way, it is.
don't even know why I'm bothering to write this since it's not going to change Riot's matchmaking approach at all, but whatever I guess.
There are plenty of players that are better than their current division and don't belong at a certain rank, but feel like they are stuck. They aren't challenger smurfs rocking an 80% winrate all the way to Diamond, but they may be a few divisions or even a tier above their counterparts, and can easily attain a 55% winrate on some of their best champs.
The problem is that, Riot's matchmaking system tries to 'balance out' games so that both teams have a 50% chance of winning. In other words, the system actively works against you climbing, by putting worse players on your team if you're tryharding every game, and slightly better players on your team if you are not giving a %%%%. This 'winrate bias' has been proven in other posts extensively, so I don't need to bother proving it here. Also I am multi-seasons Diamond with thousands of games played on several different accounts, so I can also say with certainty that this is true.
At a 55% winrate, you will have to play 20 games (win 11, lose 9) to gain around 40 LP, assuming a moderate LP gain of 20. So, to advance to 100 LP promos, that requires 50 games, and that only if that you're consistent, don't tilt, play your best champion, dodge trolls, don't get smurfs, etc. 50 FULL GAMES of consistent play in order to climb.
I haven't even factored in what happens when one gets trolls, afks, smurfs, tilt mode from encountering the former, OP picks on the enemy team, facing Pyke 3 games in a row, and general mistakes that can further influence your winrate and create loss streaks.
And at a 51-52% winrate, you're essentially hardstuck, gaining 40 LP every 100 games (51 wins, 49 losses) , or 40 LP every 50 games (52 wins, 48 losses), which is 250 games per division at 51% winrate, and 125 games per division at 52% winrate. Don't even bother trying to climb if you have no champions with a winrate above 53%.
Given that the average game length below Diamond is just about 29 minutes per game, that makes (29 * 50) / 60 = 24.16 hours of gameplay, or 1450 minutes of time.
If we assume that the average player plays 3 hours per day, it will take a week and a half to climb ONE division. And that's when this player is playing his or her best, EVERY SINGLE GAME.
But then we have promos, which statistically you have a 40% chance of winning (if not less). You have one game that is almost balanced but the enemy team is slightly better, one game where the enemy is way better than your team, and one game that your team is slightly better than most of the enemy except for 1 or 2 players. (In no particular order).
If you lose promos with double loss, (L - L - /) you're back at ~65 LP.
Which statistically means you might be in for another 20 games (at a 55% winrate) to gain that LP you unfairly lost (unless you get lucky and win 2 in a row)
If you lose promos with double loss, but one win (L - W - L), you're at ~81-88 LP. Same rules apply.
So if you're feeling like you're in ELO hell, you're probably right. Try changing your approach. The system will not allow you to climb quickly unless you are 1v9 hardcarrying every game. Climbing is a marathon, not a sprint, but it is doable.