The first thing to say is that this is a tragedy, first and foremost, with some comic elements.
Because it seems to be described in many places as a comedy movie, which, along with the whimsical movie poster, might give you this impression that this is a going to be a feel-good experience.
But no; while it has some funny jokes, they basically finish up by the middle of the movie and the rest is just a succession of appalling things being said and done.
It's a morality tale; some relatively relateable characters start by telling white lies for the greater good but end up digging themselves into ever worsening problems.
And herein lies the main issue I have: you can have a comedy movie where everything goes wrong: a black comedy.
But if there's no humor and you're making an outright tragedy, then you need some other elements to sustain such a story. Here, it feels like they make a point by the end of the first act, and then that point just gets repeated, more and more painfully, through the second and third acts with little entertainment value.
The 4 stars are because the acting is very good.