>>712880714I'll go even further and say that the true intent of the Genocide Route isn't about the nature of violence in video games and how you're a bad person if you enjoy it, but more so the relationship between a player and their love for a certain video game. If you're just a casual game enjoyer or were satisfied with the game on a regular playthrough, you'll probably stop at Pacifist. If you're someone who loves Undertale and wants to squeeze every drop of content out of it though, there'll almost certainly do Genocide. The real thing being drawn to attention is not how much you enjoy violence, but how much you enjoy the game. You just spent the entire game befriending and saving these characters from a fate of eternal imprisonment, yet now you're murdering them all just to get more of the game.
Of course, there are some people who are uncomfortable doing this and just watch it on Youtube (Flowey even comments on this type of player near the Sans boss fight) but some people legitimately don't care and continue destroying the characters they love, all to squeeze some additional content out of the game. It's just commentary on how weird 100% completion in a video game is, especially those with morality choices and alternate pathways where bad things happens to the characters.
You're also rewarded with the two hardest bosses in the game, which to me signifies that it was made with the intention of it being the last route you take care in the game for people either itching a challenge or the game going "alright, you should know the ins and outs of the gameplay by now, it's time to test your abilities".