Yeah, ROOM SERVICE only suffers if you start comparing it with other better movies in the Marx stable, but it's pretty entertaining in its own right (unlike CIRCUS, WEST, STORE, and NIGHT IN CASABLANCA). Attempting to shoehorn the Marxes into a pre-developed script that wasn't written for them sounds like a blueprint for disaster, but not only does it work (mostly), it gives the movie a unique feel that makes it an interesting outlier in Marx canon.
Come to think about it, I wonder if ROOM SERVICE was actually improved by the fact that it was written Marx-blind. One of the reasons that some of their other scripts of this period were so poor is that they were too self-conscious of what the Marx Brothers were supposed to be about, if that makes sense. By this time Harpo had devolved from the escaped lunatic of the Paramount days to the cutsie, lovable scamp of the MGM era, Groucho and Chico were being written as comic heroes (contrary to their original characterizations), and the goal of the scripts was always for the Brothers to make things right for the young lovers. ROOM SERVICE, by accident of the prepackaged script, allowed them to play a version of their original characters again, completely devoid of altruistic motivation and totally out for themselves. It's nice that RKO came along and gave us a Marx Brothers movie like that in the middle of all those sappy MGM pictures.