The planet is literally a mudhole bc of all the rain. It is brought up numerous times. They are in an open hole in this place, while it is raining. The poor conditions are to show that Han was sent to one of the worst places he could go (a pointless battlefront full of slaughter that is just an awful place to be) and that the wookiee prisoner is being imprisoned in unliveable conditions and is being fed other prisoners.
Hope that helps.
My objection to the aesthetics of the muddy scene weren’t because I thought it didn’t fit or didn’t make sense. I just really disliked it. Although I hope my rational is relatable, my previous post was meant to be more of a “fan-boy rant” than a “coherent review”. I promise I’m not attempting to change anyone’s minds. 😉