Let's not say "postmodernism" like it's a bad thing, first of all. Without postmodernism there'd be no Hitchhiker's Guide to the Galaxy, House of Leaves, White Teeth, Written on the Body, The Man in the High Castle etc. I feel like the OP doesn't know what s/he's referencing by calling out that particular literary genre. It's a style designed to make us question the nature of reality, truth, and humanity. As such, it can be a pretty powerful tool.
Take, for instance, Bodahn's speech about the Hero of Ferelden when we encounter him for the first time in the Hightown markets. There's a moment where he stops talking to Hawke, looks out at the screen, and addresses the player instead. This is a scene where the game is working on two levels: one in which Hawke as the character is receiving relevant information to the world, and one in which the player is hearing about their own past accomplishments.
In some ways, most video games are "postmodern" to an extent. Anytime you have a tutorial level, anytime there's a reference to another series, the game is suggesting that what's going on inside it isn't real. Well, obviously. But in most other forms of fiction, you don't often see these same shoutouts. Sometimes a character will reference feeling like they're "in a movie" (or a play or a book, etc.) which is a clue to the reader that on some level, the characters know their reality is a construct. In video games, though, it happens all the time.
What postmodernism isn't: anachronisms that result from lack of research, a catchall term to refer to anything you don't like, etc. So saying that the love interests all want to romance Hawke regardless of sexual orientation is not an example of postmodernism. It's not an example of anything, really, except that the society of Thedas is much more liberal and open regarding orientation. Not unlike ancient Greece, for instance. And you can't have anachronisms in a fantasy setting that's outside earth.
In short, I guess I'm saying I don't know what the OP is saying. You're going to find it very hard to escape postmodernism in games because the medium itself is based on those principles. Do you not like references to other games (such as the "eaten by a gru" comment one miner makes during the Deep Roads expedition)? Do you know like references to the player as a controlling entity (such as Hawke's comment that someone must have thought long and hard about his name)?