No, it's not ok. Contextually the daughters believe the world just ended because Sodom and Gomorrah were destroyed so they think they need to re-seed the world, which one might consider a justification, but the etiological purpose is to describe the origin of the Moabites and the Ammonites, who are the historical enemies of Israel, and is supposed to show how these two enemy tribes have a shameful beginning (incest). So, it's bad what they did and ew look how gross the Moabites and Ammonites are.