I think the show could have actually put the effort into developing those characters. Drogo and early Daenerys in the show might make some sense individually, but their romance is 100% nonsensical. You can't get around that. I even remember when Daenerys in the show referred to Drogo as "my sun and stars," because it was patently ridiculous. The fact that she would ever sincerely fall in love with TV show Drogo speaks to delusion or a victimization complex, not naivety.
The idea that she would go into the encounter in any mindset but abject terror
If you had a romance preceding and motivating the "encounter," you would not expect her to feel abject terror.
or that he would give the vaguest shit about acquiring consent (or even have apperception of the very concept)
Game of Thrones is all about shades of grey and about characters sometimes unexpectedly diverging from type. One should not have an allergic reaction to the idea of a Drogo with character nuance.
Cultural relativism could apply just as easily to the show's version of the scene, too. Hell, even in the real world, marital rape was legally an oxymoron in every one of the United States until the mid-'70s.
Since he's legitimately concerned with the experiences of his female characters, GRRM makes a pretty massive distinction between consent (which includes the Daenerys situation) and non-consent (which includes rape and marital rape).
The fact that marital rape is acceptable to many characters in this world means next to nothing, because GRRM is constantly making value judgments that the reader goes along with. There is a world of difference between the marital rape that Sansa almost experiences and the romance that Daenerys has with Drogo. That value judgment is made, and we're invited (rightly) to participate in making these value judgments.
It doesn't make any sense to suggest that cultural relativism covers both. Certainly the average slob in Westeros doesn't care whether Sansa is in love with Joffrey, but why should that infect our value judgments or make us less willing to make moral distinctions?
And that's really the greatest thing about Game of Thrones and this universe. It's not just about experiencing their crushing medieval existence and their various backward ways, it's about exceptional people breaking through it, finding dignity and honor by diverging. That's what draws us to the Starks, and that's obviously what Daenerys is all about.