I think I will have to disagree somewhat. Difficultly should change how you play, not how long. Needing to Grind better gear is not respecting the players time.
That said there are games I did enjoy the grind, “the world ends with you” is one of them, but that is a case of earning new ways to play in most cases.
That’s why it’s a nuclear plant instead of a wind turbine /jk