We do have more information. We know it’s based on chess elo system, and you can read more about it here:
https://www.chess.com/terms/elo-rating-chess
They have rules of thumb, such as if a player has 100 elo more than another he’s expected to win around 5/8 times (64%), or if he has 200 elo more he’s expected to win 3/4 times (75%)
In legend, at least, your rank can be a good approximation of MMR, so you can predict certain things before they happen. If you win 10 games in a row and get matched to someone with like 1k ranks more than you, you can be sure your MMR is now higher than your rank shows, but you still need to win against better players to improve that rank. If you don’t, your MMR will quickly stabilize around the rank where you are.
You can also see how dense your ranks are based on the difference in ranks of players you are matched with. If you get matched with players of similar rank (like +/- 50 ranks), it’s not very dense - this means that there’s a considerable gap in MMR between you and a player ranked 100+ better than you, so you can expect to improve ranks slowly.
If you get matched with someone 500 ranks better than you, that rank is dense, which means 1 win will get you more ranks and you can expect to improve ranks faster.
In lower ranks where you only have ranks 1 to 5 and stars, you are matched based on your previous season’s MMR placement, which is lumped in categories/baskets, meaning you can’t even get matched against people who were a lot better than you finished last season (which automatically means whole Neon’s conspiracy theory which prevents him from hitting Legend is catastrophically wrong).
If your legend climb is harder than it used to be, it’s because your expected rank once you hit legend is higher than it used to be - because your MMR is higher. Noone conspired to keep you stuck in platinum. With enough games, you’ll hit legend and get a rank close to the one you finished the last season in. If you give up, you’ll just get less stars next season, have an easier grind, but lose 3 to 10k ranks once you hit Legend and then you’ll just have to win the harder games you gave up from last season if you want to return to where you once was.
It’s all very transparent to anyone playing long enough to notice the patterns and logical enough to not allow emotions to get the better of them.