Many modern MMOGs require players to interface with the game using multiple hotbars, key bindings and macro scripting. WoW even supports a multitude of user created interface add ons. In the instance of macros and interface add ons, it often feels like you're helping to program the game to make up for it's design deficiencies. The fact that not all users utilize these optional extras can leave uninformed players at a disadvantage, especially in PvP. Macros and adons can be fun to experiment with and I'm glad that Blizzard typically supports the community of developers that create such additions to the game. But, why should players be expected to spend time researching a game's "bonus features" and assisting in its development in order to play it properly? Personally, I'd rather spend my free time actually playing the game. Is it too much to ask for a game that just freakin' works right out of the gate? A game that you don't have to modify or spend hours researching prior to playing. With DR, you can sit down for twenty minutes and enjoy some carefree hack and slash without investing hours of research in PvP strategy guides, talent calculators, quest guides, or scripting tools. You simply play a game. What a concept!
Beyond the interface complexity there are various levels of world design complexity that help to define most MMOGs. For example, most online RPGs have a a complex economy, a robust guild system, and an elaborate world that requires hours to traverse. While these elements are typically spoken of in positive terms by reviewers of MMOGs, poor implementation can make them a real drag instead of a boon. For example, the lack of a quick transit system can make a large world a burden to traverse. After the initial excitement of exploration has worn off, retreading the same areas feels like a dull waste of time. Luckily, most MMOGs learned this from Everquest and have since implemented various modes of quickly traversing the game world.
There are also standard gameplay elements that seem to be "required" of an MMOG. Gameplay elements such as reputation grinding (or faction alignment), gear acquisition and upgrades, and large party raid content are standard fare in playing an online role playing game. But are such gameplay elements and world design elements really necessary? In Dungeon Runners you don't worry about harvesting resources because there's no crafting involved. You don't worry about what items to save or what to sell at vendors because it's all vendor trash unless you use it or want to sell it directly to a player. You don't have to worry about talent trees or how you'll spec your character, or even what class to play. There are only three classes and you can cross-train class skills. If you play a warrior but decide you really like shooting lightning from your fingertips you simply buy the skill and, ta-da, you're a lightning-bolt-slinging-warrior. While playing DR, I never missed any of the world design or gameplay elements that are so often viewed as necessary to a successful MMOG.
I'm sure some players will claim that many of the elements that make a virtual world complex are the things that help make the world more enjoyable, believable, and sustainable over time. I'd definitely agree that many of the standard MMOG gameplay and design conventions are still in existence because they do work. I'm not suggesting that all future MMOGs follow the DR model. Complexity obviously has it's place. It can be enjoyable to speculate on the best way to deck out your talent tree, or to spend time crafting your own gear. But playing a simple game like Dungeon Runners has reminded me that it doesn't always have to be that way, and that there's still room for innovation in the MMOG gaming space. Simply put, having fun doesn't have to be complex. I hope that as MMOGs continue to evolve, that designers continue to look at ways to simplify our interaction with the worlds we inhabit, while retaining a sense of depth to the world and gameplay. The less we have to think about what we're doing, and the more natural it all begins to feel, the more immersive the experience becomes.
If you're looking for a quick, casual, pick up and play MMOG that also happens to be free, I would highly recommend Dungeon Runners. Its simple hack and slash style of gameplay and sense of humor make it a breath of fresh air in an MMOG universe often populated with overly complex interfaces, world design and gameplay.