We really need to do a soft MMR reset.
I'm trying not to be dramatic here, but it really feels like skill levels are all over the place. I've seen some really TERRIBLE players in higher elo (Plat / Diamond) and I've seen some INSANE players in lower elo (Silver / Gold, and I'm not talking about smurfs, these guys have ~50% winrate and hundreds of games played).
I get it, "if you keep going and you deserve it you will climb"
Of course! But on a 5 / 6 / 7 year old account, with thousands of matches of MMR calculations taken into consideration, each new game you play has less of an impact than the last on your overall MMR. A fresh account is able to climb very rapidly if the player manages to maintain a high winrate, because it has a lower number of games, so each win represents a larger percentage of total games than on an older account with several hundred or thousand games played.
I would like to suggest that everyone keep the MMR they have at the beginning of season 10, but remove the MMR history, and only track games from that point forward to calculate MMR.
This gives everyone who has drastically improved as a player over the years a chance to climb rapidly, and those who were grandfathered into a higher elo simply based on having high MMR in earlier seasons when the game was easier because players were less experienced, well... they might find that the minimum requirements to maintain whatever rank have steepened somewhat since they first reached plat / diamond / whatever.