It unnecessarily and immediately dates the game to our generation, when the vulgar words should sound archaic and more "old-fashioned" so that they fit into the fantasy setting.
Wrong. Check your history, then come back to that one. Or even, failing that, check any half decent dictionary.

The four biggest four letter words that come to mind right now are all MUCH older than, it would seem, you might think. Really. Like, hundreds and hundreds of years or more. Varying word by word, of course.
Medieval times, and well before that, people were swearing. All over the place. "Harshly", at that.

And as for real life - of the more modern variety - I think you'll find most advlts will swear, on occasion. It's nothing to do with immaturity, insecurity, or what have you. It's part of the vernacular, so it's there as an option. Particularly in times of pain, stress, surprise, shock, etc. After all, not everyone is brought up in extreme puritan fashion, with peers/environment/media/experiences/interests/activities to match, throughout a lifetime. Um, to put it mildly.