The scene where Han meets Chewbacca was covered in crap. Literally. Or at least some aggressively unpleasant looking mud. The whole visual aesthetic seemed to be to cover everything with filth because … well … I guess because they could. And because that seems to be their current approach to reinvention. In essence, take a product, cover it with extraneous junk, then falsely call it something new.
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.