Get a small, cross-disciplinary team of like... 5 developers or something. Nothing to have a noticeable impact on the rate new content is done at.

Then give them like... I don't know, two or three months to combo over old, old content. Fix bugs, make stuff interactive (like any of the three bosses in Copperbell), apply new markers for old mechanics that work in an identical way, get rid of 90% of the unnecessary prompts.

You'll get a whole lot more players not checking out, have minimal impact on the tail end of new content, and before long you have a lot more people to play with at max level if they are not dropping out during ARR as often. It seems they know this, when they made improved to the ARR MSQ and zones.