Here is why I think this movie is overrated:
The characters are unconvincing. Given that they all have an eye for exploiting other people for money, how did they become so poor in the first place, unless there was some kind of sudden divine inspiration? And is uncouth behavior all the working class would like to achieve once given the opportunity to become rich?
Although the movie seems to be compassionate with the poor as a first impression, it does the au contraire from a class perspective. The naive and gullible rich are defrauded by the covetous poor! Shouldn't be like, the rich are covetous so they have become rich?
The acting is mediocre if not bad compared to other Korean movies such as Handmaiden or 3-iron.
All in all, it is a so-so movie which nobody will lose anything if not watches.