DA2 is a sword and sorcery story, and sex and romance have been important foundations of that genre for over 500 years, that's why they should be included.
In my first playthrough, I romanced Alistair, made him King of Fereldan, and became his queen. So in my case, I'd say the sex and romance was pretty central to the story, and not tacked on. But even in a different playthrough, the Warden and his/her companions are on a life or death mission to save their world from destruction. It is perfectly feasible that people in that situation might try to find a brief moment of comfort in each other's arms. It happens in real life. (I would have liked to see other companions hook up with each other, too.) But if you didn't want a romance, you didn't have to pursue one.
I think the uncanny valley and underpants dry-humping look silly too, and would have preferred a "fade to black" a la ME2 rather than scenes that compare with Team America's, but I consider romance and sex essential to the genre as a whole.
In my first playthrough, I romanced Alistair, made him King of Fereldan, and became his queen. So in my case, I'd say the sex and romance was pretty central to the story, and not tacked on. But even in a different playthrough, the Warden and his/her companions are on a life or death mission to save their world from destruction. It is perfectly feasible that people in that situation might try to find a brief moment of comfort in each other's arms. It happens in real life. (I would have liked to see other companions hook up with each other, too.) But if you didn't want a romance, you didn't have to pursue one.
I think the uncanny valley and underpants dry-humping look silly too, and would have preferred a "fade to black" a la ME2 rather than scenes that compare with Team America's, but I consider romance and sex essential to the genre as a whole.