Its useless filler content now. The leveling grind for it is boring. I believe more players would be interested in the game if they could skip that useless content grind, and get to access to the main features from the start rather than wasting time with the 1-80 crap.
This is the issue I had with CATA.*
Blizzard spent most of the resources developing useless low level content. Revamping useless low level zones. So much wasted content on low level areas, that could have been made for endgame instead.
The levels in WoW hurt the game more than it help.*
Mentoring like Guild Wars 2 does, will be the best way to make older content more fun for all.
Or if not that, I would simply suggest getting rid of the 1-80 levels and make the game 1-10 instead. And change all low level content to max level content.