Aside from some implications (if you've read the manga), this should be spoiler-free:

Some think perfect stories need to be convoluted, twists after twist, stories need to be complex, that you get the details after you watch it a second or third time, something never seen or heard of, never even thought of.

Characters need to have a complex nature, they should be full of surprises, a mosaic. A character who just wants to see the sun, who just wants to save his sister, is not good enough, he/she should want more, because of something unthinkable that has happened in his/her past which made him the way he is. Why not get power? Why not be the strongest? Why not be the richest? Why not be some caricature of a character?

That's just not true. That necessarily doesn't make a good story and character. The best story in the world can become dull if someone unfitting tells it. And on the other side, the worst story in the world can be good if the perfect narrator tells it.

A good story is one which is narrated by the right person.

This is the case with Kimetsu no Yaiba. It is a well narrated story which focuses itself on it's small cast of characters without getting convoluted. It doesn't need to expand the world or his cast. Thankfully Gotoge never loses her focus. There doesn't need to be a bigger baddie with some insane motives after the other, like in Naruto. There doesn't need to be 100 islands with 2000 characters, like in One Piece. (I enjoyed and enjoy both series, they're good in their own regard, that's beside the point)

Once you get into the art, its very cute side-characters (those dot-eyes^^) and jokes you get absorbed into the story. The last arc was very intense for me bc i really liked the cast. Waiting for the next chapter was hard.

I'm sad that this was the last chapter but i'm happy she didn't extend the story for the sake of money and ended it perfectly. Kimetsu no Yaiba is globally acclaimed, she could have sold-out if she wanted to like many other mangaka. Thank you for not doing that.