Frank Turtletaub’s review published on Letterboxd:
When the Kims create and go through their plan to infiltrate and take over the support system of the Parks, it sort of feels like an Ocean's movie. The Kims have an elaborate plan with multiple moving parts that rely on some predictable but potentially volatile variables. Still, it goes off without a hitch.
The difference between Danny Ocean's gang and the Kims is that the former is an elite team of specialists who is looking at a payday that will secure them for life and let them live their days in luxury. The Kims are a small family that live in a semi-basement who folded pizza boxes for money. Their goal isn't to score big but to live sustainably for once, despite their current material predicament.
The skill level is the same but despite the effort the Kims are nothing but workers in the eyes of the world, to be exploited as necessary despite their skillset. The idea that they can snake their way in to the higher echelon of society should indicate their value but in reality it guarantees them nothing. For the working class, anything can disrupt the plan.
When the old housekeeper shows up at the house (currently illegally occupied by the Kims), Ki-woo mentions that this "isn't part of the plan." The hijinx that ensue threaten the newly found material wealth of the Kims, the tension building, every moment a potential reveal that could ruin their intricate plan.
Yet after that entire sequence, and despite every near miss, the rainstorm devastates their humble home and ruins all of the progress they made. Their plan has been for naught. They've been ruined. And the next day, they have to go back to work to get it all back and pretend like nothing happened. It's no wonder that Ki-taek gives in to his worst impulses.