I can’t imagine there are very many people left who could be targeted as new players. “Kids these days” aren’t really into MMOs. Animal Crossing sold 31 million copies last year - almost three times WoW’s subscriber count at its peak. And there are vast swaths of adults who are like me: folks who gave it a genuine try at some point and have no intention of going back. That’s why they released the Classic stuff - it’s easier to engender warm nostalgic fuzzies in former diehards than it is to develop a new playerbase from a game nearly old enough to vote.
MMOs are a dying genre, and WoW is ancient by the standards of any game. It doesn’t have much to offer to anyone not fueled largely by a sense of nostalgia and community. And the window for a brand new MMO has probably closed at this point, so the odds of successfully transitioning your paying customers to an entirely new one are slim.
But hell, even if their playerbase is half of what it was in 2015, it’s still printing free money for Activision/Blizzard. They’ll probably keep the servers running for another decade, until it’s in the same boat as Heroes of the Storm - sunsetted and maintained by a skeleton crew, milking out the last vestiges of microtransactions from an ever-dwindling base of loyal fans.