It might be nice to have a teammate who is thinking about what he is doing, but what I really want is a player who does not need to. A good, experienced player is not actively thinking about playing as a process. It is a series of practiced actions that fall below the conscious level, freeing his higher mental processes to think about other things, such as larger strategies or making amusing conversation during combat.
It works for anything your brain does. I am typing, but I am not consciously thinking about where the keys are on the keyboard. I just think about what words I want to type, and my fingers are already in motion. I don’t even need to think about how to spell the words that I am using. The only way this could be more efficient would be to connect my brain directly to the computer, but then I would need to develop the new neural patterns to make letters and words appear on the screen that way.
When you learned to drive, avoiding a crash and getting the levers and buttons working was enough to absorb your entire attention. Adding a passenger or a cell phone greatly increases that crash risk because you only have so much active brain to devote to a task; add more RAM.
When people crush you in FPS or RTS games, a major reason why is that they are thinking about how to beat you while you are thinking about how to play the game. You are thinking, “I am Protoss this time, so I should queue up a few probes. That is P. I’ll get my original probes going, then set a rally point over here. Great. Okay, I am in the SE corner, so I don’t have to share a secondary base spot with anyone. New probe, set him to working, and I’m not far from being able to get a gateway.” Meanwhile, your opponent’s hands are zipping through the drones he has made a thousand times while he is deciding whether to rush with zerglings or mutalisks.
That is the guy you want on your team or raid. You don’t want your healer thinking or making decisions; you want him to have made those decisions so many times that he reflexively does the right thing. You want to have people on your raid who do not need to think about how to do their parts, so that they can watch the new guys and make sure that they are doing theirs correctly. You want someone who knows the timing on his attack cycle without watching for attacks to recharge, so that he can watch for adds.
It is not that any of these tasks are hard or require that much intelligence. There are just a lot of them going on at once, and the more of them you can reduce below the level of conscious effort, the more attention you have to devote to the difficult parts. Or to making jokes.
This is why you keep practicing your kata. Most martial arts are a series of simple motions, but you need to be able to do them correctly while reacting to someone who is trying to kick you in the face. This is why you farm a thousand mobs. If you need to think about how to kill an ogre, you have not killed enough ogres.
This is why games are structured with the interesting stuff later. You have a tutorial that introduces a few things one at a time, then you start out fighting things with just a few abilities. If the game is designed perfectly, you will accumulate new skills just as you reach mastery of the old ones, and this is mastery in your brain not when the little bar stops moving on the screen. (Replay Portal with developer commentary to see this done consciously and perfectly.) You end with dozens of abilities that you will be using in concert with dozens of allies, an orchestra performing a symphony of destruction.
This is why games get boring. Once you no longer need to think about how to kill an ogre, it is somewhat less satisfying to do so. There is real joy in learning new things, even if it is as trivial as the best way to order your attacks. There is an epiphany, “I get it!” That is the best moment of gameplay you will have, but you cannot get that moment back. Falling (back) into your groove is the closest thing, which is more comfortable but less euphoric. And killing the next 1000 ogres will not involve any meaningful mental activity, so it is pure grind unless something else spices it up.
This is why advanced features trip you up. Give me an encounter that violates the normal pattern of gameplay. Take the normal actions that we do reflexively and have them lead to painful death. You must learn something new. You must think. Now you have an interesting encounter.
Until that one goes on “farm status” too.