I think the ‘authentic’ experience went from grinding with a purpose – levels, gear, gold, mount, etc. To grinding for the sake of grinding, BUT, we’re going to time gate the grinding you can do, so it artificially takes longer to reach your end-goal.
Everquest was grindy as fuck… for XP. But, you didn’t mind it, because you were always grinding with a group, and every DING was like an orgasm. Then WoW came along, and there were more grinds. Hell, I spent about 2 or 3 weeks in the Plaguelands cemetery grinding gold for my epic mount. But, when I got it, I was ecstatic!
Then, everything changed…
Grinding in WoW now is: doing X amount of repetitive daily quests for reputations. Reputations that time gate items that are useless to you, once you have the reputation for them. But, you need the reputations to advance your level in whatever treadmill mini-game that expansion has: Artifact Power, Covenant Levels, etc. Which you need to get maxed in order to be accepted into groups to do higher level content.
Oh, and BTW, all that grinding becomes completely worthless once then new expansion comes out, because no content in WoW ever incorporates previous content or achievements.