Except LFR has nearly no mechanics, doesn’t require any buffs. Even if these raids aren’t as hard as we once remember them; they still require that you stay out of X, get Y debuff has to be removed or Z run away from the raid to not wipe your raid. Also consumables weren’t often used by the average player in 2004-2006. The average player would dump their potentially better blue item for a epic that actually isn’t better for their class in 2004-2006.
I am sure AQ40 and BWL and Naxx will be plenty hard for casuals, similar to probably normal/heroic mode in modern wow.