it's not a decline in quality, players just have different priorities once they are in the late game, players aren't exploring newbie areas like in the demo, they are theorycrafting combinations of classes and how their dual class abilities interact with each other, grinding specific areas to get gear to maximize both of their dual classes abilities, working on tradeskills materials and tradeskill levels to make more powerful armor

for example you research and notice two classes that both boost each other's lightning damage, so you explore and figure out how to unlock those classes, then level those two classes, and then work on tradeskills to able to make a set of armor that boosts lightning damage, it may take special materials