Kinda the same way you explain the history of the US to someone in their 20’s since they don’t seem to be teaching US history in school anymore. Really, 1000 students from Harvard were asked who George Washington was and more than 60% thought he was some sports figure. SMDH.
Okay, now that I have that out of my system, you really can’t expain WoW lore to a new player because the lore changes every time you check it.
Semper Fi! 
Well, honestly, you probably shouldn’t even worry about it.
The current dev team doesn’t seem to be.
Show them the definition of “retcon” and explain that it happens all the time and they shouldn’t get too attached to anything. Also, say to not invest in liking any main lore characters as they will eventually be done dirty by the writing. And yeah, I’m looking at you, the person who came up with the way Vol’jin died. 
Have her watch videos on Youtube about the lore. There’s a couple that has a channel, doesn’t play the game, but is very much into the lore.