It's been a long time since I've played WoW, but if I remember correctly, most of the vanilla grinds you listed were intended for entire guilds or servers, so it limited the impact on individual players, and/or forced individuals to group up (the entire purpose of MMOs), making the grind more fun.

The guild I was in grinded the hell out of Molten Core, other events, and materials to equip just one of our warrior tanks with the legendary sword (can't remember the name). It was a big achievement for us (a non-hardcore guild) and really fun to do. We were just stepping our toes into Blackwing Lair when TBC released.

Unfortunately, post vanilla WoW, the grind was codified into the individual gameplay loop, making it boring and unfun. I hate describing things in terms of feelings, but it best encapsulates the experience: vanilla was really fun and felt like a lived in world, post vanilla felt like a 2nd job. Even with all the shiny new stuff post vanilla, it never captured the magic that vanilla did. Even the woefully ridiculous 12-48 hour long 40v40 Alterac Valley PvP matches, where you could fight for hours in a stalemate, log off and go to sleep, go to work the next day, come home, log back in, and get into the same Alterac Valley match, felt really epic, stupidly funny, and fun. Now (last time I logged in), all AV matches are rushes to the end, with the Horde and Alliance just running past each other with minimal PvP.

The vanilla devs felt like they just wanted to make a good game. Post vanilla, it felt like WoW, and every other MMO, just wanted to pad out player game time. It's why I no longer play MMOs, or any other game that has a hint of padding in it. It's stupid and anti-player.