The FL acts like a bully, it's painful to watch that. She has no charm or intellect, I sure hope she will never be an announcer.
The first ML was very very good and at ease in his role in Hospital Playlist, but this role doesn't use his natural abilities - he is a great singer and dancer, great with kid actors, and his jokes land perfectly. This role is something else - I've never seen anything as tastless as trying to combine cancer hospital visits with slapstick. Eww. And the other ML was a great Greatest Deliveryman, but he is totally unrelatable as a chaebol boss. He is very good at looking nice and schoolboyish, but bosses very seldom look like that. Also, the dress he made didn't flatter the FL's skin tone and was too big for her. That is a mistake I've never seen in a K-Drama before.
The older charcters, mom, grandma, sister-in-law and the impotent cook are a bit more interesting and also very good looking, so I will finish this for their sake.