Another thing they did well, IMO: Like a lot of MCU films (especially Infinity War and Endgame), they were able to cover a lot of ground by having a lot of scenes do more than one thing. For example...
*********SPOILERS (not going to use tiny font anymore since this is a dedicated thread, so people should know to look for spoiler tags if they don't want things ruined)****************
This may seem like an odd example, but the bathroom shows up a couple of times, and each scene has at least a couple of different things going on that move the story forward on a couple of different levels.
The first time, Han Mi-nyeo tricks the guards into letting her go so she can sneak a smoke, and Sae-Byeok sneaks in to spy out that the guards are cooking the honeycomb for the next game. It seems like the scene is important because Sae-Byeok has stumbled upon something, and we wonder what the guards were cooking. When that ultimately doesn't really go anywhere, the scene may either be forgotten or feel like just a throwaway. We don't know whether they are cooking drugs, or poison, or some concoction of body parts, or what. We can later put together that it is honeycomb, and it kinda feels like..."oh, that's it?" The scene isn't that important on its own. But it does several small things:
-For nonwesterners who actually knew what honeycomb is ahead of time (not me), it forshadows the next game.
-It gives us a bit of character development: It sets up Sae-Byeok as brave and proactive about her situation. It also further sets up Mi-Nyeo as an unlikeable character who is kinda gross and willing to break or disregard the rules if she thinks she can get something out of it.
-It sets up the location for the more important second time we see that location, and helps us understand and not question how Mi-Nyeo and Deok-Su can be alone there later on.
So while it almost seems like a plot dead end that ended up being abandoned (I know that I mistakenly thought that this would be the first of many attempts by the main characters to infiltrate the operation and spy things out to either gain advantages or to blow up the games), it actually does fill some valuable roles.
The second time we see the bathroom, it also manages to accomplish more than one thing:
-The most obvious is that it sets up both of those characters are mercenaries in their own way, and foreshadows that Mi-Nyeo will kill Deok-Su. Related to that, it also sets up the betrayal in the tug-o-war episode, and somewhat raises the stakes.
-The location itself (and, by extension, the fact that the characters are having sex there) serves to subliminally convey that these are a couple of gross, disgusting people.