It's not like Kiiara wrote the song (most likely). She's probably just asked to sing a part so i don't know why the hate. She has a decent voice. How can it be so bad? Just wait for the song first.
You know you can hover your mouse on the thing to see parts where Chester is, like 1:03:27 for example, instead of watching the video from beginning to end lol. And no, it's not a pro shot.