Recently I've been in a bit of a war with myself about game design.
I create a lot of prototypes - typically at least one a week. For a long time, they were mostly about exploring some gameplay idea - a particular tweak on poker rules, or a feel for the timing in a brawler.
As time passed, I became steadily more interested in themes. Pick a theme, then craft the rules out of the giant backlog of gameplay I explored. Fit them together.
In the end, there are only a few kinds of play that are considered "valid". If I come up with a theme such as "fluffy bunnies in the woods", it'll have to rely on the same challenges that every other game relies on.
Movement and timing. Pattern recognition/optimization. Choosing the right option out of an ever-changing crowd of options. Luck.
There are some games that people barely consider games. For example, Gone Home.
But Gone Home still uses these mechanics. You move around the house looking for things to click on. You put together the pattern of the story in your head. The least gamey game is still reliant on the same challenges as the most gamey game, just with very different pacing.
What about Animal Crossing and similar games?
Well, there's a lot of pattern recognition and optimization in Animal Crossing - gathering valuable things, hitting the parts of the town you need to hit, tending your crops, finding jobs and sidequests. Those are all pattern recognition and optimization.
There are some things peeking from the shadows, though. Creating your character involves picking from a list of options, but unlike an RPG battle or math-teaching game, none of the choices is right or wrong. Similarly, in Gone Home the challenges are all about movement and clicking just like in a shooty game, but none of the movement or clicks could really be considered "bad". You can't lose at Gone Home - the challenges just serve to to indicate which way is forward so you can control your own experience a bit more clearly.
In both cases, the "challenge" (picking an option, moving and looking) is there to allow the player to control their own experience. In both cases, the game tells you how to move forward specifically so you can linger or move on as your preferences and mood dictate.
OK, with that in mind, let's back up a little bit.
Gameplay is really boring.
Oh, it can keep your mind entrained. I play Kerbal and Skyrim and so on. The mechanics keep me thinking, keep me looking towards the next step.
But when I look at it, there's nothing to the mechanics at all. My outlook on life wouldn't be any different if I couldn't choose the right amount of fuel and thrust to land on a fake moon, or level up my sneak enough to stab a fake skeleton with a fake knife.
There is some value in these games, though.
Through Kerbal I learned a lot about the mechanics of space flight. While the lessons are stilted and simplified, they further my interest in and my understanding of real science, real space flight. By giving me a cartoonish version of something real, the game lets me hold it in my hands, twist it, hold it up to the light, and start to understand.
Skyrim is not so positive. The cartoonish thing Skyrim lets me hold is the culture that formed it. It's a very manly-man Tolkien fantasy with a lot of serious issues. But it serves: when I hold Skyrim in my hand and start gluing other people's pieces onto it, I can see all the weaknesses in that culture, and explore my steadily-increasing distance from it.
Even if you don't read into it as much as I do, Skyrim's strength is the setting, not the mechanics. High-fidelity fantasy world you can wander around in? That's what you'll remember about Skyrim. You won't fondly remember the lockpicking puzzle.
So, why do we do it?
Why do we slap useless gameplay into these things?
1) Pacing. By keeping the mind engaged, players can remain interested in the world even when their preferences aren't lining up and they aren't interested in the bit of setting they're currently looking at.
2) Engagement. By allowing players to choose how they approach the game, we also change how they approach the setpieces. This helps players grip the concepts in the world and hold them up to the light.
3) Synchronization. By giving all players the same emergent tools, we allow every player to have their own unique experiences with the same foundation. Sharing those experiences with other players (or themselves in the past), we allow players to have conversations about the concepts in the game. Even if it's just bragging about headshot counts.
Thinking about gameplay from this perspective is very freeing.
Instead of thinking "what kind of gameplay do I want in this game?" maybe we should think -
1) How do I pace the game so that the player remains interested even when their mood drifts out of synch with the setting?
2) How do I let the player explore the ramifications of change in this world?
3) What commonalities do I rely on to help players understand each other's experiences and choices?
I haven't gotten any further than that, yet.