I can think of several ways to keep the old world relevant - many which happened in the very expansion we’re now on the tail-end of. It’s not impossible to shake things up in an interesting way, but I’ll grant that seeing the same scenery day in and day out can get tiring.
However, these new places have little to no connection to the rest of the world in which they exist - which was my point. They may as well be their own game, for all they have to do with everything else.
Everything that comes before them ends up existing purely to get you to that content - and now, with every major patch being essentially self-contained, that’s even more evident. It’s great to have some place new to explore, but I think there’s a balance they can strike - one they’re missing the mark on.