The matchmaker does not have to be fair and unbiased to produce the results we are seeing, both as the players who can consistantly climb and those who feel it is rigged. I present the following two hypotheses as a more eloquent and believable way of summarizing the complaints:
-MMR is actually the standard deviation from your rank’s average performance, not your position within the ladder as a whole. We know MMR is measured as a standard deviation, but Blizzard has not explicitly stated that it is a single value that is consistant across all ranks.
-Matchmaker will attempt to balance based on MMR in a way such that both teams have equal chance to win.
We know Blizzard keeps an incredible amount of stats. We know your SR gains and losses are largely effected by where they believe you belong. With that in mind, it would be very feasible for MMR to track your performance relative to your rank and create a value for use in handicapping.
Thus, if you have a very low MMR, such as when actively throwing or when playing in a rank much higher than you belong, you make it harder to make a fair match. This will result in either seeing more frequent throwers on the opposing team, or more frequent carry players on your own team, which should push you back toward the median. If you continue to lose these games, you’ll drop hard, but most players will get a bit of a bounce back because their performance will be better in such a game. This is why you don’t straight drop, even if you’re ranked above where you belong.
On the flip side, straight climbing will test you harder by either sandbagging you with players who have relatively low MMR or matching you against smurfs or other overperformers. If you are able to still contribute, you will get reasonable PBSR losses(or pull out some wins) in these circumstances and continue to climb. Your MMR will regress to the mean as the games are harder and your performance is not as outstanding. Then, you start the cycle over. This is why climbing is rarely a straight streak of wins with 70%+ winrate unless you’re truly much better than your rank.
New players should, by reasonable standards, quickly drop to low silver or bronze with 20% winrates just due to lack of awareness on hero interactions, maps, etc. That isn’t what most people experience, and it’s incredibly hard to get a winrate below 25% or above 75% for any reasonable time period.
None of this has been explicitly denied by Blizzard, and you’ll notice that the shills like Xion typically skip over any post that attempts to explain how it could exist, instead choosing to argue with the bottom of the barrel posters that think they are masters players hardstuck in gold. It does not have to be anywhere near as severe as people like to think for it to be a significant reduction in enjoyability and game quality.
There is plenty of reason for a system like this to exist, and components of it are documented in patents owned by Blizzard. It would reduce ladder mobility, but it creates addictive tendencies. You may want to believe game designers have the single intent of creating a fair and balanced game, but the truth is that they are tasked with creating a game that generates revenue. The two goals may overlap at times, but make no mistake, they will give up fairness for cash every time.