To me scaling ruined the leveling experience. Thankfully before it came out I had one of every class at 100 or higher. There is nothing fun, engaging, or emersive having the everything in the world level up with you. You don’t feel like your getting stronger in fact while leveling you actually end up getting weaker since the moment you level up your secondary percentages go down.
I know it won’t happen but the best way to make leveling fun again would be to have new areas to level in. Even though cata revamped leveling and many zones did change significantly you still are fighting a lot of the same enemies, doing alot of the same quests, and looking at similar (or close to it) terrain.
Would also be nice after leveling dozens of times now if you could fly in vanilla content at lower level. Another thing I don’t see happening but as old of content as vanilla is don’t see the harm.