old server pop doesnt matter in your statement because ppl didnt used to get world buffs the way we do now. It was far more rare and never all of them. 2019 classic was a redo of 2004 and it was pretty good. Only downside was it was so solved everyone had world buffs for raid, raid logging, etc whereas originally it was far more organic.
Can’t do that today with a small team. They had a big team back then. Vanilla is appealing, even as a re-release in classic, because its the classic MMO formula. Guilds, grinding, weapon skills, talent trees, professions, social situations, limited and scarce loot, but with a 1.5 (or 1.0) sec gcd and very little actual twitch gameplay. Its the MMO of the times. Modernly retail is an action RNG that you sometimes see other players in. The traditional MMO formula that was forming around the early 2000s is absent.
In the playthrough, TBC keeps most of them, Wrath starts to shed many (but it was still so good people overlook it) and then by Cata people really start to see that the traditional MMO stuff is mostly gone, and it doesnt have the aura of WOTLK to cover it up. personally I still really liked Cata is a game, its not until around WoD that you truly strip mine the game of MMO features.