Why do you guys keep on saying it’s not the same as the novel?

I read in a forum that the overall tone and mood of the webtoon is just much more moodier and darker than the tone of the novel.

On the 6th page, around the 7th or 8th post there is some discussion about the differences between novel and webtoon.
https://www.novelupdatesforum.com/threads/my-in-laws-are-obsessed-with-me.122095/page-6