I get it. I spent the better part of months on the Marshall Windsor quest in BRD because I autistically refused to leave a zone until every quest was done (had Loremaster already complete when they added achievements). Shit I even did most of the Cenarion Circle grind in Silithus solo because TBC had launched and rendered old world barren.

That's why I enjoyed MoP. It was a lot slower but still progressing in its design. It stuck that good point between the "clear your entire day" difficult of release Cata/TBC but not complete faceroll of Wrath. The dungeons were still doable, but you had to be competent and able to do mechanics regardless.

And Challenge Mode was phenomenally fun, simply because it was 100% optional. Not "optional" like every other mechanic in the game was, but optional in that you gained nothing but a mount and a cosmetic armor set from it. No recipes, no gear, just something you did for fun with the boys.

I played that game from mid Vanilla until early Legion, and was even a hardcore raider spending 8+ hours a day from late TBC until MoP ended. And I truly think MoP was the peak of the game portion of it. Vanilla and parts of TBC had that "soul" to the world that filled it with wonder, but those fucking Pandas managed to strike the balance between being fun and what was left of that soul.

Also I think the problem with Cata was they spent so much time redoing all of the vanilla zones that anyone who wasn't a brand new player was left with a fraction of the dev time left for the end game experience. The dungeons and raids were fun enough, but there was nothing outside of them.