There can be an argument made that Warcraft was never in-fact classic fantasy, given the complex machines from WC2-3, but overall, the themes and tropes still aligned with the classic style of fantasy.
WoW maintained the fantasy style of play for a while. BC introduced us to space travel, MoP/WoD industrialized warfare and Legion, well Legion we were launching from our intergalactic space ship to land planet side to take on demons.
How would you describe the thematic / genre style of WoW to someone who hasn't played?