Hidden mmr was originally introduced as an attempt to counteract the smurfs in games. For instance, if a diamond 1 player dropped down to gold, they would play other diamond 1 players 'labled' as gold instead of actual gold players because the system would recognize your higher mmr. This way higher mmr players always stay out of lower ranks. It sounds like a great solution at first, but it comes with a huge cost.

The problem is this: if you play poorly and derank a bit, it is VERY difficult and tedious to rank back up again. This is because even if you deranked a tier, you will still play against players who have the skill level of the tier you were playing at previously. The only difference is their fake "lable" of a rank. Mentally this can be very difficult to deal with, as players think they're playing much worse and not improving but in reality they're playing with people the same skill level who also went on a losing streak and deranked.

I personally experienced this. First act of the game I was d1, then d3, then immortal a couple times including this act. I lost a ton of games because I played very poorly a couple days, and now I'm stuck in low diamond/plat3 going against other ex immortals

In my opinion skill level should always be represented by what rank you are, it should never be a hidden value that the player cannot see. I don't think this even helped for smurfing in the first place. I appreciate the devs for the attempt but I personally am hoping for hidden mmr to leave forever by next act