I agree with torrit (and probably the majority of players) that the high level story is pretty shit. They've been repeating the same two storylines of "THIS CHARACTER IS NOW EVIL YOU MUST STOP THEM" and "VANQUISH AN ANCIENT EVIL" for an extremely long time. However, I still think it's really cool to explore the zones, complete some of the quests (even though lots are along the lines of 'slay ten draco-boars for their gallbladders'), and immerse yourself in the world. Lots of people who have been playing for a long time lose sight of that, but it's still a very real appeal for a lot of players.
Right now you can level to 20 without paying anything so I'd try that and see if you like it. If you do, I'd recommend subscribing and maybe trying wow classic too, but don't buy the current expansion pack. It's not very good and the next expansion pack is coming out before the end of the year so you'll just end up wasting money.