People tend to confuse ease of use with difficulty. It's easy for a game designer to just say "it's hard because they'll have a hard time figuring out the controls" or "they'll have a hard time finding this one ring in the room", but honestly, that's just bad game design. If the objectives were in real life, then sure, hide and seek questing is a good idea. But when your interactivity with the world is limited to a mouse and keyboard, you can't force the player to make actions that challenge his familiarity with the system.

It's best to make the actual game elements more difficult, so let's say, harder packs of mobs, or specific items that need to be used at correct times, since they build on what the player can do in the world and how he interacts with it already.

I've seen a lot of games where people would say "This game is hard and a challenge" when in reality the controls are just bad and unresponsive. Making quests more accessible and easy to go through helps you focus more on your actual combat skills and class mechanics rather than spending 10 minutes hovering over the area with your mouse looking for something.