I mean they already said how it would be calculated, and that's solely based on medal score.

All the people in favor of the new patch and competitive BGs have been trying to promote a better MMR system based on win loss, at the very least, and @ZOS_Kevin commented that they are taking this into account, but nothing has been changed so far and hope looks slim.

It isn't even as bad as you portray it though. In most games a person who wins 93% of their matches will have a high MMR, but someone as you stated, with a 57% win rate can out rank them if they just play enough, because for most games a win generally gets you about as much MMR as a loss would remove, so as long as you are winning over 50% you will still climb, but the reality is much worse. Someone with a 0%, literally 0% win rate can be the top stop. Realistically winning 0% of your matches and having the highest spot is unlikely, but something like a 30% win rate can still be top of the leaderboards as long as they play more often and some medal score because winning means absolutely nothing based on what we were told.