Just keep re-releasing vanilla,tbc,wotlk every few years under the idea of "FRESH START!!!!!!" to give people the dose of nostalgia like half the failed korean mmorpgs.
I genuinely miss the old dungeons that f2p players que up to, I always hated Blizard for limiting us in those 2 BFA dungeons.
Especially Shadow Fang Keep, loved the moment when I got Nightreaver years ago and never again.