For those who can't climb because they keep getting bad teams
If 2 teams are equally good, they'll have 50% win chance against eachother. If one of those teams gets a player that's significantly better (because he's actually better than his rating says), then that team will have a higher win chance. A higher win chance doesn't mean that you'll win that game, but if you play a lot of games, it does mean you have a higher winrate. A higher winrate means that your rating will rise. Eventually, you're not better than your rating suggests anymore and you will have a normal win chance and winrate again and your MMR will stagnate.
In reality, both teams aren't equally good because
- It's hard to find people with exactly the same MMR. The system will adjust for this by giving the underdog team more MMR gain for a win and less for a loss and vice versa for the team that has a higher win chance (based on MMR).
- MMR is never an exact indicator of one's skill or performance. Not only is this because it requires a LOT of games to evaluate someone correctly, but also because human performances are very variable and one day a player can play really good while playing really bad the next day (or game). Also, if people are forced into a role they don't main, they will probably play worse (on average, in some cases they play better because they play safer).
This means that even though you are higher skilled than your MMR suggests, there could be a player in your team with lower skill than his MMR suggests. There could also be a player in your team who is last pick forced into ADC and sucks with it. There can also be a player who is having a bad day or is playing in conditions that aren't optimal (for example playing while ill). This will hinder your smooth climb.
BUT all of this is random stuff and random stuff go both ways. These players can be in your team or the other team, also undervalued players can be in both teams. In the end, all of this randomness WILL even out. For some people the luck-badluck evens eachother out from the very beginning and only has a marginal impact, but sometimes you will have consistent badluck for 50 games with only a few spikes of good luck and you'll have to play atleast 100 games for it to even out. Complaining won't help though. The only thing that helps is play more games for a bigger sample. If you keep getting badluck, maybe you should reconsider whether it's really badluck or just something that isn't random but caused by yourself. A great example of this is the presence of flamers or AFKers. Some people complain that they are consistently queued up with these guys, but very often are they causing or stimulating this themselves. Also, people with the "screw you, I'm first pick" mentality will have bad teammates much more often than those who listen to their teammates, check their lolking, and give up their position if the others would do better in it/worse in the position they'd otherwise be put in. I can't count the amount of times I allowed Riven mains to go top even though their winrate was only slightly above 50% with riven while my wukong winrate was 70+%, but they barely played games as other lanes so they'd naturally do worse when forced into it.
