You have some wrong assumptions about the Ranked system. Let me try to clarify.
All of this you can read up on the Wikipedia Article about the Elo Rating System
We know from previous systems and they 'fathers' that the first few games are weight heavier into you Ranking.
So you being in bronze but belonging somewhere completely different is very unlikely already, but it can and will happen and has happend. The easiest solution would be to keep weighing the next few games after your promos still a little more compared to regular games. From Riots we know, they have systems to identify smurfs and put them into their respective MMR very fast.
We don't know how the system works, but we can assume a very simple solution. When you get placed in a lower MMR than your skill level would allow you for, you will start to win and win big. It would be very easy to seek out for accounts on X games winning streak and just modify their MMR-calculation to have bigger fluctuation. This would be achieved by just switching out one variable. Should be easy enough. How exactly it works we don't know but just seeing how fast some smurfs rise will tell you it works.
So there are checks and balances and even without these checks and balances you will rise to your MMR it will just take longer, but when you are better than the people you are matched with you should win vastly more than you lose and thus keep rising till you hit your acutall skill level and start losing more.
With this we come to the next wrong assumption of yours.
the game decides that my win rate is too high.
This never happens. As I said. it is a mathematical certainty that you will go roughly 50/50.
The game decides nothing. The game sees you MMR and matches you with players of that MMR, when you win a lot, your MMR rises, thus the MMR of players you are matched with/against does to. At some point you reached your skill cap. At this point all the people in your match are as good/bad as you are. Playing against people of similar skill will always lead to you losing. It feels like losing more at first, because due to human perception bias it feels like only losing. Sometimes you also are only losing, you just hit a losing streak it happens. This is the nature of gaming. You will not win los win lose win lose... etc you sometimes you win a bunch and lose a bunch and sometimes you get really lucky and win games against people better than you, your MMR now outgrew your skill, the next enemies are bnetter than you and you are out of luck and start losing until you face enemys that are at your or under your skill level and you start winning again.
So a ranking system, which then is used to match you with players of similar ranks will with mathematical certainty always hover around 50/50 win los ratio. Only for the best of the best this does not apply anymore. Since there is nobody left to beat them they will go higher than 50 and the worst of the worst have nobody to win against, nobody is as bad or worse than them so they will lose more than 50/50.
The problematic thing is partially the human perception bias. And the reset at the season beginng plays part too. Also as Riot admitted there was some trouble with matching the LP gains and ranks to the right MMR brackets. This meant that people with low MMR would gain more LP per win and lose less and thus they would climb in ranks. They looked like high skilled players but they were not and their MMR was not the MMR of a high skilled player. This is why we Gold in Iron games and Irons in Diamond games during preseason and early season. Riot fixed it but it takes some time for these players to lose the gained LP again.
Also coming back to the bias thing. Humans tend to focus on negative things (evolutionary thing that helped to learn prevent life threatening dangers) So we look up matches we lost and focus on the players in the enemy team that were better than us, we rarely look up the skill of players in a game we stomped and even less often matches in which out team carried us. So go through your match history and have a look how often you played with Gold 2 instead of against. How often you were placed in a match below your skill group and especially how often you beat these gold 2 players. You will be surprised.
TL:DR
The system works in a way that will even out at 50% win los ratio, this is not coded in, it just is a side effect of a fair enviornement. Some of this years changes with the Ladder make it appear like the match making is massively out of whack. This will even out in the next couple weeks. The human perception bias makes you focus on the negative stuff so you leave out games you profit and stomp people. Losing games is natural when you are not the best of the beast, the one that cannot be beaten.
The MMR system is way more complicated than you think, but you can be certain there is no hard code for a 50/50 win lose ratio, it is a side effect of the system and this side effect actually is good even though it feels bad.
