What gave that film the extra twist it needed was that it focussed on an ex-junkie's attempts to extort a million dollars from the city in return for his knowledge of the critter's whereabouts. In The Stuff , somebody is marketing a dessert product that is actually a parasite which takes over the bodies of those who eat too much of it. Since one of its early effects is to make you crave more of it, that isn't too hard. The perspective in The Stuff is from the point of view of an industrial spy hired by the ice cream companies to find out where the Stuff is coming from. Since Cohen came up with the basic idea and wrote the screenplay, he receives both credit and blame for it.
Credit is due for the dialog and some of the characters.
Blame accrues for the poor plotting. Cohen has three or four really good ideas, but he doesn't develop any of them very well. Practically as soon as he presents one of them, he speeds off to the next, as if he expected the audience to fill in all the details for him. He is very good with characters, but not too good with action or suspense. His editing style is peculiar.