I've been going through Zak Smith's old posts about rules and it's slow going because blogspot is not exactly designed to be easy to navigate older entries, but it's worth it to delve into his blog-dungeon because it tells me a lot more about how Zak thinks and why he sometimes says some of the stuff he says. In other words, context!
He's got a post where he defines D&D as a list of some core things that are basically expected when you ask somebody with some tabletop gaming experience to play D&D with you. It's an insightful post about the D&D system that delves into what I like to think of as the philosophy of D&D, but will usually just refer to as "rules wankery" at the table.
Anyway, go there, read that, then come back and read my diametrically opposed list of what makes a game not D&D:
1. Characters are of one race (human?) and there are no classes.
2. How do you define who is specialized with fighting or sneaky shit? Skills. Everybody has the same pool of skills. Nothing special or restricted.
3. No levels, and no experience points. Skills and abilities go up through random chance.
4. Only 4 ability scores and you match them with the suits from a deck of cards. No numbers.
5. There are no spell lists, because there's no magic.
6. The game is set in an approximation of New Zealand in the future, they are now a global superpower that took over the world. There are lots of floating cities surrounding the island as well. The players are high-ranking members of the new world order nobility.
7. What's armor class? You won't be hitting anything because you can't fight. Everybody in the world has been implanted with brainchips by the NSA, who now work for New Zealand, and everybody is forced to be cheerful. Being nonchalant is as rude as it gets. The only way to really hurt someone is to steal from them, thievery hasn't been chipped, only violence.
8. Physical damage is recorded as a word. You're either Alive, Sick, Injured, or have Hurt Feelings. You can be Dead too, but then you'd have to make a new character.
9. There is no attacking, but if you want to steal from somebody you draw a card from a standard deck of 54 cards (with 2 Jokers). There is a simple matrix for determining if you succeed at any particular action, and a slightly more complex matrix for opposed actions.
10. There are no levels and no hit points. Increasing skills simply widens your effect on the action matrix.
This almost sounds like a Cyberpunkish hack for In A Wicked Age.
And no I wouldn't enjoy that. I once described In A Wicked Age as a game set in the world of Conan where players are controlling the characters that Conan kills.