It’s clear that WoW’s current content is event-based - things are broken up into seasons and seasons into patches that has some kind of event or another. You login and you are shepherded to the latest event. By the time you are done with the current event, a new event happens.
Levelling is seen by many as a chore that must be done before you can play the event-based “real game” hence said people just rush through it.
Instead of wasting all that effort only to annoy players why not create “levelling content” that is played in parallel with the event-based content. It would be “exploratory” content to flesh out the world that players can play at their own pace - or not at all if they don’t give a rat’s bottom.
Said content will reward borrowed power that works in said content’s area, transmog, conveniences (like transportation options), mounts, and of course gold.
It’s a pretty big change from how Blizzard traditionally does things but it’s worth a considering IMHO.