I think the praise for Mendy is a bit OTT. When I watch Mendy I see a player who's first thought is to pass it back or sideways to the player nearest him. Hardly a crucial element to the team, doing a job Matty James or King did all the time also.
People say, "he didn't put a foot wrong today", or "he keeps things ticking over nicely and keeps it simple". Its not hard to 'not put a foot wrong all game' if you only pass sideways and backwards.
I may be in the minority but I want a cm who has more to his game than being a steady and safe player. Take creativity like Maddison or Tielemans out and we have a serious problem. Take out Mendy and literally any player who can complete a short sideways pass could take his place. I honestly would rather have kept King and let Mendy go, King has history and an affinity with the club, Mendy would be proud of his short sideways passing, but he also scores important goals.