I want to play a video game. When I load into an instance, I don't want to press random buttons for 10 minutes and get a reward, that's not playing. If there's no difficulty, there's no game. Unless like cookie clicker is your thing I guess? Or idle games?
The dungeons, trials, and raids were fun. They made me actually pay attention to the game, instead of considering pulling up youtube.
They were also easy enough that wiping is a surprise. I think it's at a good medium between "difficult enough to be interesting, easy enough that almost anyone can do it".