The "git gud" posts here are amusing but they are pretty disingenuous. While I don't think anyone will deny your player skill is ultimately what decides a portion of your rank there are many outer influences that direct it. This is a blizzard game after all so if you wanna solo queue you have to be prepared for little Timmy. Little Timmy doesn't care about group comp, he doesn't ever pick a healer or tank no he eats paint chips and plays genii because OMGWTFBBQ I AM NINJA. This is the case in every Bliz game wether it's LFR or Ranked HoTS or ranked Overwatch. While it's true some can grind out of MMR hell even if they are a better player than their rank let's assume a 60% win ratio overall. In many cases that still ends up needing to play hundreds of rounds to grind out of the stupid leagues.
I have made some progress grinding up already but the KOTH being fucked explains a lot.
That's not unique to Blizzard games, sorry to inform you. And it also doesn't affect the reality of the situation. There's DECADES of data and statistics behind ELO systems and MMR, and unless Blizzard decided to ignore all of it (including what they've used and learned from over a decade of having ranked systems in almost every one of their games) it's all still applicable. There are maybe one in a million people who are truly outliers where the random factors add up and screw them for an extended period of time, but that's probably really close to ACTUALLY one in a million people.
This is the problem with all these debates, is they're not really debates... we know how human psychology works in these setups, we know how the statistics and data add up. The whole reason ranking systems are designed the way they are today is to appeal to our psychology and keep people playing, even when the front end doesn't represent the back end (League's system is a gigantic example of this). If you have a 51% win rate, you will climb, slowly but you will climb. All that takes is you being better, on average, than your opponents.
Remember that the enemy team actually has a HIGHER vulnerability to the randomness you bitch about because it's 6 randoms, whereas there's only 5 on your team. Which means if you truly are better than your opponents, you will win more games. People bitch about the random factors holding them back in every game since forever but it actually doesn't add up to reality when you consider that fact. Once again, the only 100% stable factor in your solo queue games is you.
Edit: Another way to consider that last point is that, if everyone complaining about DCs/Genji-wang-doodles on their team holding them back was actually correct, then you would be GUARANTEED to advance because your opposing team will always have 6 of those people, whereas you only have 5. The only excuse then becomes that the system is rigged against YOU especially for some reason, giving you a higher likelihood of spazoids on your team, which is obviously and blatantly not true for any of us. Thus, the problem is still... you.