Comment by cosmic_cheese

As a current (albeit casual) player of mainline WoW, I think its biggest problem is how hard it's locked itself into the idea of what an expansion should be. Every expansion has more or less followed the TBC playbook: higher level cap, new landmasses and instanced content, total gear reset.

Of course it's going to become impossible to keep everything relevant when they keep stacking the tower higher for decades.

There's no reason why an expansion couldn't expand on what's already there instead of throwing everything out. They could for example do an expansion that fleshes out current zones that could use more love and expands the game horizontally. That doesn't mean they have to abandon the TBC model, but even if they'd just gone with a repeating pattern of "horizontal-vertical" with expansion releases they'd have a lot less content to try to juggle.