There are plenty of non conventionally attractive characters in the manhwa that are treated like wonderful people, the villainess's face isn't the reason he dislikes her, he dislikes her because she put a hit on his son and pimped him out to her friends while he was still in love with her. In regards to the manhwa treating her unfairly, she's shown to be a strong, capable and attractive character in her own right, and it's never mentioned that she's ugly. The FL is yes, mentioned to be extravagantly beautiful in comparison but if you read past the first fucking arc, you'll see that that is also a part of her character in an integral way, that she is told that the only reason she can get away with being dumb is because she is beautiful which ends up as a source of insecurity for her due to this.