One of the important aspects of gameplay is user interface. Although it may look extremely complex at first, with various options and tools in front of you just as you start, it is learnable and the player gradually gets used to it. Take Eve Online for example. The user interface is extremely complex, however but one is introduced to elements slowly though the tutorial, and gradually gets used to it by trying out different things. By finally understanding the complex user interface, the user is able to do many different things in the game. However, clunky interfaces causes the game difficult to manage and run, thus draining the fun. Players do not want to have trouble controlling characters, perform basic tasks, or deal with the UI that is not very clear or responsive.
One thing I think games need to avoid is oversimplication. A game should not be so simple that it leaves the players bored and disappointment. The first example that comes to mind is Spore. I loved it so much at the beginning, controlling my sea creature was so much fun but then it gradually become more and more tedious for me. I just didn’t want to touch it after awhile.
Gameplay elements should be considered. There should be several in order to allow for more things for the player to do. At the start, I would not want to be completely overwhelmed, so I would not expect everything to hit me all at once. How the player would respond to the game, especially psychologically, should be taken into consideration while designing the gameplay.