Echo those who feel your S will need to do his best to make do for the time being and to focus on finding social activities/friends outside the dorm.
IMO, it’s unlikely he’ll get them to change at this point considering they’ve been together for at least a semester and trying to get them to clean up will create more enmity between them and your S as their mental/verbal response to that would be along the lines of “Who died and made you dad/king?!! Shove off!!”
A former post-college roommate who was an extreme neatnik in his room recounted having such responses tossed at him when he tried getting more messy roommates to clean common areas of their rented apartment more to his standards*.
- By the time we became acquainted and shared the same apartment after our undergrads, he has accepted the fact it wasn't the best plan to even suggest keeping common areas clean to his high standards....especially considering most of our roommates were medical residents/interns who were rarely home and would be so exhausted from punishingly long work shifts they'd literally go right into their rooms and sleep.
Out of curiosity, did your D2 accommodate that request, ignore it, or even told her to “Figure it out yourself?”
Had an older college friend who tried pulling a variant of that on his post-college roommates because he didn’t know how to do basic household chores tasks like changing lightbulbs.
Said roommates who were already not kindly disposed to him due to his tendency to be argumentative and thinking too highly of himself despite not having the bona-fides to match(placed on academic suspension back in undergrad and not discreet enough to keep that info to himself when not necessary to disclose) responded along the lines of “Hey [name of older college friend], if you were smart enough to be admitted to and graduate from Oberlin, you should be smart enough to figure out how to do it yourself.”
Said older friend felt they were being extremely mean and should have accommodated his request. Had to break it to him that not only was his assessment of the situation completely off the mark…but that he was making a serious imposition on roommates who were already not kindly disposed to him due to his past behavior/actions and further outing himself as someone lacking basic life skills. .