Actually, even the default graphics could still have visual appeal. Watching the trees come into bloom in the spring, perhaps, or spectating as a squad takes apart some captured goblins in the pitting chamber, or micromanaging a Miner's careful breach of a volcano to feed your magma industries.
But DF's real strength is in the stories. I see the trailer as being mostly audio, of users orally relating very brief sound bites of some of the more awesome/funny/ridiculous things that have happened to them, or just facts about the game in general.
"Dwarf Fortress is the only game where you can stab someone in the pancreas, perform surgery on a pancreas, and then cook & eat pancreas."
"So, somehow, my duke able to fit his entire head--with helmet--inside a goblin's mouth, and bite out one of the goblin's back teeth."
"Do you always look at it encoded?"
"Well, you have to, the game's still in alpha. Me, I-I don't even see the code. I just see Horse, Carpenter, magnetite . . . "
"This moving blob of purple is miasma, the stench of a decaying corpse. Look, see, the dwarves that had to walk nearby are annoyed & disgusted by it."
"Yeah, I've made plenty of mugs for my dwarves to drink from, but most of them get ignored--everyone wants to drink using the artifact mug."
"And then there's that time that a Miner fell in love with a guy, during the act of beating him to death . . . "
"Say, what's that green stuff over there? Grass? It wasn't there before."
"No, that's, uh . . . vomit. Yeah, that's dwarf vomit."
"That's disgusting. Tell me more."
etc.